Boeing

B737-300/400/500
(CFM56-3)
Issue: 1AUG2006
Author: NeA

ATA 23 For Training Purposes Only

LTT 2006

Communications

EASA Part-66
B1

B737-3_23_B1
Training Manual

For training purposes and internal use only.

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Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500

23−00

ATA 23 COMMUNICATIONS
Revision-date: Feb. 15, 2007
FOR TRAINING PURPOSES ONLY!

FRA US/T-4 NeA Jan 29, 2007 ATA DOC Page 1

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
GENERAL
23−00

23−00 GENERAL
The audio integrating system provides a communication link between the flight
compartment crew members, cabin crew members, ground crew members,
airplane radio systems and recorders.
The ACPs (Audio Control Panels) permit selection of the function desired.
The position of switches and potentiometers are transmitted digitally from the
ACPs to the REU (Remote Electronics Unit).
Audio from communication and navigation systems and from the audio selector
panels are integrated at the REU.
Audio from the ACPs is also sent to the voice recorder system via the REU.
The REU contains amplifiers for the flight interphone system, the service
interphone system with the capability of controlling the gain of each system.
It also contains a tongenerator for the altitude alert warning and discrete
grounds for the flight recorder.
In case of a failure in the Captains or F/O’s ACP or in the associated
REU-circuit audio switching relays allow the connenction to the observer
interphone system.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Sep 15, 2006 02/FLT−INT GEN/L1 Page 2

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COMMUNICATIONS B737−300/400/500
GENERAL
23−00

 
    
!"  
 
   
    

     # 

     

     
    

 
 
      
!"  


    
   
 # 
    
           
  
   
! 
!"  
 !
  
FOR TRAINING PURPOSES ONLY!

 
 
 
     
  !    

   

          

        

Figure 1 AUDIO INTEGRATING - GENERAL
FRA US/T NM Sep 15, 2006 02/FLT−INT GEN/L1 Page 3
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GENERAL
23−00

THIS PAGE INTENTIONALLY LEFT BLANK

FOR TRAINING PURPOSES ONLY!

FRA US/T NM Sep 15, 2006 02/FLT−INT GEN/L1 Page 4

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COMMUNICATIONS B737−300/400/500
GENERAL
23−00

AUDIO COMPONENTS

PRESS-TO- HEADBAND
TALK
SWITCH

EARPIECE

TRANSDUCERS AMPLIFIER

ACOUSTIC
TUBE
FOR TRAINING PURPOSES ONLY!

HANDHELD MICROPHONE OXYGEN MASK NOISE-COMPENSATED HEADSET HEADPHONE

WITH BOOM MICROPHONE

Figure 2 Audio Components

FRA US/T NM Sep 15, 2006 02/FLT−INT GEN/L1 Page 5
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COMMUNICATIONS B737−300/400/500
GENERAL
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AUDIO CONTROL PANEL GENERAL DESCRIPTION

GENERAL
(Config 1)
The ACP enables the flight crewmembers to transmit and receive on the radio
communication systems, communicate using the flight and service interphone
systems and make announcements over the PA system.
Airplane navigation systems can also be monitered.
Three ACPs are located in the flight compartment.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Sep 15, 2006 03/ACP/L1 Page 6

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COMMUNICATIONS B737−300/400/500
GENERAL
23−00

MICROPHONE SELECT
PUSHBUTTON

VHF−1 VHF−2 HF INT CABIN PA

LISTEN LED
BOOM/OXYGEN SELECT GREEN
SWITCH
BOOM

OXY
RAD/INT PTT
SWITCH
VOICE RADIO
ONLY
FOR TRAINING PURPOSES ONLY!

SPKR MKR ADF 1−NAV−2 INT

LISTEN ON/OFF AND VOICE FILTER

−CONTROL SWITCHES SWITCH

Figure 3 AUDIO CONTROL PANEL Introduction (CONFIG 1)

FRA US/T NM Sep 15, 2006 03/ACP/L1 Page 7
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COMMUNICATIONS B737−300/400/500
GENERAL
23−00
(ConfigG 2)
The front panel of the audio selector panel has the following switches:

Microphone Selector Switches RADIO − INT PTT Switch

The microphone selector switches are used to connect the boom, The RADIO − INT PTT Switch is a system keying switch.
oxygen mask, or hand microphone to the interphone, passenger address (PA), When in the RADIO position the switch will key the communications system
or any of the selectable transmitters. selected by the microphone selector into transmit.
The microphone selector switches are momentary contact switches. When in the INT position the switch will key the flight interphone system into
The switches are mechanically and electronically interlocked to permit only one transmit regardless of the microphone selection.
switch to be selected at a time. This switch is spring loaded to center off.
A light in each switch comes on when the switch is selected, and the related The PTT switch on the ASP is connected in parallel to the PTT switch on the
receive audio channel will become active. control wheel which serves a similiar function.
The microphone selector switches are split legend switches used for both The flight deck speakers are muted when the microphone with the exception of
microphone selection and call indication. the oxygen mask microphone is keyed at the audio selector panel, at the
The upper half of the switch, when turned on, indicates the microphone control wheels, or at the hand microphone.
selection made.
The lower half of the switch, when ”C” is showing, indicates an incoming call for VOICE ONLY Select Switch
that system.
The VOICE ONLY select switch is a momentary contact switch.
When active (the switch is lighted), the voice filter attenuates 1020 Hz,
Volume Control Switches switching out DME ident.
The switches are turned ON/OFF by pushing the switch knob.
The switches control the selection and volume level of the received audio. SPKR/ NAV Selector Switch
The control switches turn clockwise for increasing volume and The SPKR switch is the off−on/volume control for the interphone
counterclockwise for decreasing volume. speaker. This control is not used on the observer audio selector panel.
The NAV switches are used to select the navigation system for monitoring.
Listen ON - green LED Any number of the switch may be selected at the same time permitting the
FOR TRAINING PURPOSES ONLY!

monitoring of more than one system.

OXYGEN PRESSURE SWITCH

If the oxygen mask is out of its stowage box, the left box-door activates the
oxygen shut-off valve. This allows oxygen to stream into the mask.
A pressure switch sense pressure. This signal is sent ot the audio control
panel, which provides this signal to the remote electronics unit.
The remote electronics unit now disables the boom-set mike and activates the
oxygen mask mike.

FRA US/T NM Sep 15, 2006 03/ACP/L1 Page 8

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COMMUNICATIONS B737−300/400/500
GENERAL
23−00
FOR TRAINING PURPOSES ONLY!

OXYGEN PRESS SW.

OXYGEN STOWAGE BOX

Figure 4 AUDIO CONTROL PANEL - (CONFIG 2)

FRA US/T NM Sep 15, 2006 03/ACP/L1 Page 9
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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEM
23−51

23−51 FLIGHT INTERPHONE SYSTEM

SYSTEM PRESENTATION
General
The flight interphone system provides the flight crew with capabilities to The audio selected by the first observer is heard at both observer stations.
communicate with each other and provides the means for them to transmit and Ground crew personnel access the flight interphone system by plugging a
receive on airplane communication radio systems and receive on airplane handset into the flight interphone jack on external power receptacle panel.
navigation radio systems.
This allow the ground crew to communicate with the flight crew.
The flight interphone system consists of:
 audio selector panels, Power
 a remote electronic unit, The flight interphone system receives dual power source of
 jack panels,  28v DC battery bus and
 push−to−talk (PTT) switches on the control wheel,  28v DC bus No. 2,
 handheld microphones, through circuit breakers and diodes to allow either bus to power all circuits on
load control center P6.
 headsets,
 boom microphone/headsets
 oxygen mask microphones, and
 loudspeakers.
The captain and first officer each have:
 an audio selector panel,
 a cockpit speaker,
 a control wheel PTT switch,
 a boom microphone headset and
 oxygen mask microphone, plus
FOR TRAINING PURPOSES ONLY!

 jacks for a headset and

 a handheld microphone.
The first observer has:
 an audio selector panel,
 an oxygen mask microphone,
 a handheld microphone and a headphone.
The second observer has a headphone jack.

FRA US/T NM Sep 15, 2006 04/FLT−INT DESCR/L2 Page 10

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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEM
23−51

MIKE MIKE

INT INT

CAPTAINS STATION 1. OBSERVERS STATION FIRST OFFICERS STATION

VHF−1VHF−2 HF INT CABIN PA VHF−1VHF−2 HF INT CABIN PA VHF−1VHF−2 HF INT CABIN PA

BOOM BOOM
OXYGEN BOOM OXYGEN
MASK MASK
STOWAGE OXY OXY STOWAGE OXY
VOICE RADIO HEAD-PH VOICE
ONLY
RADIO VOICE
ONLY
RADIO
ONLY
HAND-M
SPKR MKR ADF 1−NAV−2 INT
MASK-M SPKR MKR ADF 1−NAV−2 INT HANDMIKE SPKR MKR ADF 1−NAV−2 INT
HANDMIKE
HEADPHONE HEADPHONE
BOOMSET -H DPH BOOMSET -H DPH
PWR BOOMSET-MIKE PWR
BOOMSET-MIKE PWR HEAD-PH
OXYG-MASK MIKE MIKE- CLOCK OXYG-MASK MIKE CLOCK
CLOCK JACK MIKE /-
RADIO
RADIO
X 2. OBSERVER PTT X PTT
X
MIKE /- CAPT FO
RADIO ON OBS ON OBS
PTT
FOR TRAINING PURPOSES ONLY!

NU NU
CAPT INPH 2
1
28VDC PWR (A21) CAPT AUDIO LEGEND:
BUS2 NORMAL NORMAL
ONLY WITH CONFIG 2 ASPs
F/O INPH 2
1
F/O AUDIO
THIS WIRE IS ONLY INSATL-
PWR (D21) COMM RAD LED ON D-ABXW AND ON
NAV RAD
ON DATA-BUS:
SERV INT CVR
CAPT BAT INPH
PWR (A20) OBS AUDIO SWITCH PA - AMPL X -MIKE SELECT
28V DC -LISTEN ON/OFF/VOL
BAT BUS GPWS -SPKR ON/OFF/VOL
SERV FWD / FLT TCAS -BOOM/OXYG MIKE SEL.
F/O BAT INPH INPH AND
PWR (D20) WARN (20) INT AFT INT DFCS -INT PTT FOR BOOM/OXYG
JACKS ATT JACKS (ONLY ON D-ABXW AND ON
P6−2 CIRCUIT BREAKER PANEL
Figure 5 Flight Interphone-Architecture
FRA US/T NM Sep 15, 2006 04/FLT−INT DESCR/L2 Page 11
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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEM
23−51
Flight Interphone System Operational Use
Selection of which system will receive the microphone input from each flight
crew station is made at the audio selector panel.
The last MIC SELECTOR pushbutton which is pushed will determine the
communication system to be keyed by a PTT switch at that flight crew station.
Flight crewmembers access the flight interphone system to communicate with
each other by setting the PTT switch on the ASP to INT or I/C position.
The PTT function can also be performed at either pilot’s station by setting the
control wheel PTT switch to the INT position.
Flight crewmembers key a selected airplane radio system from an audio
selector panel by pushing and rotating the system audio control and pushing
the system MIC SELECTOR switch and then holding the R/T−I/C or
RADIO− INT switch to the R/T or RADIO position.
This connects the boom or oxygen mask microphone and a control line to the
selected radio system.
The PTT function can also be completed at either pilot’s station by holding the
control wheel PTT switch to the MIC position.
All flight compartment PTT switches are connected to a speaker mute line so
both cockpit speakers will be muted when a PTT switch is actuated.
No speaker mute happens if the MASK-BOOM switch is in the MASK position
or oxygen mask is in use.
This prevents audio feedback from the speakers to the microphones.
All audio warning messages from ground proximity and altitude alert are heard
by all flight crewmembers without being selected on the audio selector panel.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Sep 15, 2006 04/FLT−INT DESCR/L2 Page 12

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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEM
23−51

VHF−1 VHF−2 HF INT CABIN PA

3
BOOM

OXY

VOICE RADIO
ONLY

SPKR MKR ADF 1−NAV−2 INT

1
FOR TRAINING PURPOSES ONLY!

1 PANELS WITHOUT CALL (C) INDICATORS

2 PANELS WITH CALL (C) INDICATORS 2
3 PANELS WITH HF RADIO

Figure 6 Flight Interphone Activation on ACP

FRA US/T NM Sep 15, 2006 04/FLT−INT DESCR/L2 Page 13
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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEM
23−51

OXYGEN MASK MICROPHONES PRESENTATION

Audio selector panels without a BOOM/OXY switch.
The switch for selecting the oxygen mask microphone is in the oxygen mask
stowage box.
When the mask is packed the switch is positioned to the boom position.
Removing the mask from the stowage box will automatically position the switch
to the OXY position to select the oxygen mask microphone as the operating
microphone at that crewmember’s station.
The boom microphone can be returned to operational status by:
 repacking the mask in the stowage box,
 closing the compartment doors, and
 activating the compartment ”PUSH TO TEST AND RESET” button or by
 closing the mask stowage compartment left door and activating the
compartment ”PUSH TO TEST AND RESET” button.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Sep 15, 2006 04/FLT−INT DESCR/L2 Page 14

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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEM
23−51

VHF−1 VHF−2 HF INT CABIN PA

BOOM

OXY

VOICE RADIO
ONLY

SPKR MKR ADF 1−NAV−2 INT

RESET OXYGEN
TEST MASK
AUDIO SELECTOR PANEL (CONFIG 1)
100%
PUSH
INT
FOR TRAINING PURPOSES ONLY!

MASK STOWAGE BOX

AUDIO SELECTOR PANEL (CONFIG 2)

Figure 7 Oxygen Mask Mike Operation
FRA US/T NM Sep 15, 2006 04/FLT−INT DESCR/L2 Page 15
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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEMS
23−51

POWER SUPPLY
General
Power for the flight interphone system comes through circuit breakers in the
P6—2 circuit breaker panel.
The REU has three station cards and an AAU (Audio Accessory Unit) card.
Each card has a power supply for internal operation.
The station cards supply 15V DC to the ACP (Audio Control Panels).

Circuit Breaker
The CAPT AUDIO circuit breaker supplies 28V DC to the captain station card
in the remote electronics unit.
The captain station card supplies 15V DC to the captain ACP.
The F/O AUDIO circuit breaker supplies 28V DC to the first officer station card
in the remote electronics unit.
The F/O station card supplies 15V DC to the first officer ACP.
The OBS AUDIO circuit breaker supplies 28V DC to the observer station card
in the remote electronics unit.
The observer station card supplies 15V DC to the observer ACP.
Master Dim and Test
Each ACP gets 28V DC from the MD&T (Master dim and Test) system when
the BRT/DIM/TEST switch on the captains main instrument panel is in the BRT
position, and 16V DC when the switch is in the DIM position.
This voltage supplies power for the lamps in the mic selector switches.
Panel Lighting
FOR TRAINING PURPOSES ONLY!

Each ACP gets 5V AC from the airplane electrical system to supply power for
the edge lit panel lighting.

FRA US/T NM Nov 21, 2006 05/PWR INTERF/23−51/L2 Page 16

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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEMS
23−51

15V DC

CAPT INPH CAPT AUDIO 15V POWER

2 PWR AUDIO
SELECT SUPPLY CAPT ACP
RELAY CAPTAIN STATION CARD
28V DC „CAPT ON
BUS 2 OBS“

15V DC

F/O INPH F/O AUDIO 15V POWER

2 PWR AUDIO SUPPLY F/O ACP
SELECT
RELAY FIRST OFFICER STATION CARD
„FO ON
OBS“
15V DC

CAPT BAT OBS AUDIO 15V POWER

INPH PWR SUPPLY OBS ACP
OBSERVER STATION CARD 5V AC
28V DC
BAT BUS
CONTROL STAND
FOR TRAINING PURPOSES ONLY!

LIGHTING

F/O BAT INPH AND WARN

INPH PWR 28/16V
DC
AUDIO ACCESSORY UNIT CARD
MASTER DIM
P6−2 CIRCUIT BREAKER PANEL REMOTE ELECTRONICS UNIT & TEST

Figure 8 Flight Interphone-Power Supply

FRA US/T NM Nov 21, 2006 05/PWR INTERF/23−51/L2 Page 17
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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEMS
23−51

PRESENTATION OF PTT-SWITCHES
Purpose Description and Controls
The control wheel PTT switch gives push−to−talk input for the boom or oxygen The control wheel PTT switch is a three position switch. It is on the outboard
mask microphones. horn of the captain’s and the first officer’s control wheel.
These are the switch positions:
General
 MIC − microphone audio and PTT signals go to the communication system
These components send a push−to−talk (PTT) signal to the REU:
you select
 ACP radio−intercom PTT switches
 OFF − The ACP PTT switch can key the microphone
 Control wheel PTT switches
 INT − microphone audio goes to the flight interphone system
 Hand microphone PTT switches. (ACP selection is not changed).
Set the radio−intercom PTT switch on the ACP to R/T to send a PTT signal to The switch is spring loaded to the middle OFF position.
a communications system.
The switch is spring loaded to the middle OFF position from the MIC position.
Set the switch to I/C to talk on the flight interphone system.
ATTENTION: It is locked in the INT position until selected to either OFF or
Set the control wheel PPT switch to MIC to send a PTT signal to a
MIC.
communications system.
This is because of the „hot mike-function“ of the boom/oxygen
Set the switch to INT to talk on the flight interphone system. mike for voice recording purposes.
The observer can only send a PTT from the hand microphone or ACP.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Nov 21, 2006 05/PWR INTERF/23−51/L2 Page 18

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COMMUNICATIONS B737−300/400/500
FLIGHT INTERPHONE SYSTEMS
23−51

1−NAV−2 AUDIO
SELECT
RELAY
„FO ON
R/T MASK OBS“
R/T
R/T−PTT

I/C BOOM MUX ACP DATA

I/C
AUDIO CONTROL PANEL (ACP) HAND MIC PTT

F/O ACP

F/O HAND MIC F/O STATION CARD

PTT SWITCH INT

MIC SAME AS F/O

F/O CONTROL WHEEL

MIC SWITCH CAPTAIN STATION CARD

F/O CONTROL WHEEL

R/T
R/T−PTT
FOR TRAINING PURPOSES ONLY!

MUX ACP DATA

I/C
1−NAV−2
HAND MIC PTT
OBSERVER ACP
R/T MASK
OBSERVER OBSERVER STATION CARD
HAND MIC
I/C BOOM
REMOTE ELECTRONICS UNIT
AUDIO CONTROL PANEL (ACP)
Figure 9 Flight Interphone-PTT Function
FRA US/T NM Nov 21, 2006 05/PWR INTERF/23−51/L2 Page 19
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COMMUNICATIONS B737−300/400/500
AUDIO INTEGRATING
23−51

FLIGHT INTERPHONE - LOCATIONS

AUDIO
CAPT F/O
ON OBS ON OBS F/O FLIGHT
NORMAL INTERPHONE SPEAKER

AUDIO SELECT SWITCH

CAPT FLIGHT
INTERPHONE SPEAKER
F/O JACKS
CAPT JACKS − BOOM MICROPHONE
− BOOM MICROPHONE − HEADPHONE
− HEADPHONE

CAPT CONTROL
WHEEL MIC SWITCH
F/O CONTROL
WHEEL MIC SWITCH
CAPT JACKS
− HAND MICROPHONE F/O JACKS
− HAND MICROPHONE
− MASK MICROPHONE
− MASK MICROPHONE
FOR TRAINING PURPOSES ONLY!

VHF−1VHF−2 HF INT CABIN PA

3
BOOM

P8 AFT ELECTRONIC PANEL

OXY
− CAPT AUDIO CONTROL PANEL
VOICE RADIO
ONLY − F/O AUDIO CONTROL PANEL
− OBSERVER AUDIO CONTROL PANEL
SPKR MKR ADF 1−NAV−2 INT

Figure 10 FLT Interphone - FLT Deck Location

FRA US/T NM Nov 21, 2006 06/LOC/L2 Page 20
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COMMUNICATIONS B737−300/400/500
AUDIO INTEGRATING
23−51

INTERPHONE CIRCUIT BREAKERS

LOAD CONTROL CENTER: P6−1

EXTERNAL POWER
PANEL

AUDIO SELECT
RELAYS

E+E COMPARTMENT
FLIGHT INTERPHONE:
-- HANDMIKE
EXTERNAL – HEADPHONE)
POWER INTERPHONE
FOR TRAINING PURPOSES ONLY!

PARKING
CONN FLIGHT BRAKE
SERVICE
NOSE
WHEEL WELL
PILOT
ON
NORM
NOT CALL LIGHT
IN USE

EXTERNAL POWER PANEL REMOTE ELECTRONICS UNIT

Figure 11 FLT Interphone-Component Location (other Areas)
FRA US/T NM Nov 21, 2006 06/LOC/L2 Page 21
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COMMUNICATIONS B737−300/400/500
SERVICE INTERPHONE
23−41

23−41 SERVICE INTERPHONE SYSTEM

GENERAL DESCRIPTION The button on a press−to−talk type handset completes only the microphone
circuits when it is pressed; receiver circuits are connected directly to the
The service interphone system provides interphone communications between system.
the flight crew, the attendants, and ground crew personnel.
The system includes: the remote electronics unit, the service interphone Operational Use
switch, the attendants handsets, and the service interphone jacks. Push the CABIN switch and the respective LISTEN switch on the ACP.
Also, there is a provision for a control stand handset. Handsets are installed in Setting the service interphone switch (on the aft overhead panel P5) to ON
the forward and aft attendant panels for communication between attendants. connects the microphone circuits from the external service interphone jacks to
Switched service interphone jacks located throughout the airplane are for use the interphone amplifier.
by ground crew personnel during servicing and maintenance. This allows ground crew at the various maintenance locations to talk with each
Personnel in the control cabin can communicate with the attendants or ground other. Attendants may communicate with each other, with the flight crew, and
crew personnel through the audio selector panels and the headphones and with the ground crew, by using the handsets installed at their stations.
microphones of the flight interphone system.
The service interphone system gets power from the 28v DC battery bus and
also the unswitchable electronics bus No. 2, through the INTPH AND
WARNING circuit breaker located on the load control center−right panel, P6.
The remote electronic unit (REU) is installed on the E2−1 shelf of the electronic
equipment rack which includes an AAU card.
The AAU card provides the necessary DC voltage to the system microphones
and amplifies the audio signal.
Automatic level control ensures a constant output regardless of the number of VHF−1 VHF−2 HF INT CABIN PA
microphones connected to the system.
3
Since the system has no on−off switch, it will operate whenever the battery bus
BOOM
or DC bus No. 2 has power.
Gain controls for the service interphone system are on the audio control panel.
FOR TRAINING PURPOSES ONLY!

The service interphone switch is located on the aft overhead panel P5.
In the ON position, the switch connects the microphone lines from the external OXY
service interphone jacks to the input of the interphone amplifiers.
VOICE RADIO
The OFF position disconnects the microphone lines to isolate the external ONLY
service interphone jacks during flight.
The handset may be of the press−to−use or press−to−talk type.
The button on a press−to−use type handset completes both microphone and SPKR MKR ADF 1−NAV−2 INT
receiver audio circuits when the handset button is pressed.
AUDIO CONTROL PANEL

FRA US/T NM Nov 21, 2006 08/SERV−INT GEN/L2 Page 22

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COMMUNICATIONS B737−300/400/500
SERVICE INTERPHONE
23−41

28V DC T RIGHT WING REFUELING

R
BAT. BUS S STATION (STA 78)
FLIGHT INTERPHONE SYSTEM:
INPH PWR INPH AMPL T RIGHT WHEEL WELL
AND WARNING MIKE INPUT FROM CABIN-SERV INT R
F/O BAT. S (STA 655)
28V DC - CAPT LISTEN
- FO LEFT WHEEL WELL
BUS 2 INPH PWR T
- OBS STATION CARD R
F/O NO. 2 BUS S (STA 655)
T APU
R
P6−2 CIRCUIT BREAKER PANEL S (STA 1040)
SERVICE
INTERPHONE T
R AFT CABIN
EXTERNAL S (STA 1004)
AUDIO
T ELECTRONIC
R
S EQUIPMENT RACK
(STA 350)
SERVICE
INTERPHONE
ATTENDANT’S
AUDIO

PHONE HI
MIKE INPUT CABIN-SERV INT PHONE LO
LISTEN
MIC HI
MIC LO
AAU CARD
P13 FORWARD ATTENDANT’S PANEL
M1353 REMOTE ELECTRONICS UNIT (E2−1)

SERVICE PHONE HI
FOR TRAINING PURPOSES ONLY!

INTERPHONE PHONE LO
MIC HI
MIC LO
OFF
P14 AFT ATTENDANT’S PANEL
ON
SERVICE PHONE HI
INTERPHONE SWITCH
PHONE LO
(P5 AFT)
MIC HI
MIC LO
P8 CONTROL STAND − AFT FACE

Figure 12 Service Interphone-Schematic

FRA US/T NM Nov 21, 2006 08/SERV−INT GEN/L2 Page 23
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COMMUNICATIONS B737−300/400/500
SERVICE INTERPHONE
23−41

SERVICE INTERPHONE - LOCATION

SERVICE
INTERPHONE
OFF

ON
HANDSET AT AFT
ATTENDANT’S PANEL
SERVICE INTERPHONE SWITCH

SERVICE REMOTE
INTERPHONE ELECTRONICS
SWITCH
UNIT
AFT OVERHEAD PANEL, P5 HANDSET AT FORWARD
ATTENDANT’S PANEL
LOAD CONTROL
CENTER, P6−2

HANDSET JACK ON ATTENDANT’S HANDSET

FOR TRAINING PURPOSES ONLY!

CONTROL STAND −
AFT FACE

REMOTE ELECTRONICS UNIT

Figure 13 Service Interphone/Component Location

FRA US/T NM Nov 21, 2006 09/SERV−INT LOC/L2 Page 24
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COMMUNICATIONS B737−300/400/500
SERVICE INTERPHONE
23−41

CODE LOCATION AREA

A WING REFUELING STATION EXTERNAL

B FORWARD OF RIGHT WHEEL WELL EXTERNAL
C FORWARD OF LEFT WHEEL WELL EXTERNAL
D AFT CABIN CEILING INTERNAL
E APU ACCESS PANEL EXTERNAL A
F ELECTRONICS RACK INTERNAL

B D
F C E

STA STA STA

130 350 STA 1043
STA 1004
FOR TRAINING PURPOSES ONLY!

664

D
E
F
B,C
Figure 14 SERVICE INTERPHONE-JACKS LOCATION
FRA US/T NM Nov 21, 2006 09/SERV−INT LOC/L2 Page 25
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
FLT/GRD CREW CALL SYSTEM
23−43

23−43 FLT/GND CREW CALL

GENERAL DESCRIPTION
The flight and ground crew call system provides for call signals between Attendant Call
 the flight compartment and cabin attendant stations, between Pressing the ATTEND call switch on the forward overhead panel P5
 the flight compartment and ground personnel, and between applies 28v DC power to the pink attendant call lights, to the R380 attendant
call relay, and to the chime in PA amplifier.
 cabin attendant stations.
The PA amplifier sounds a high-low chime through the PA system.
The system is used to signal personnel that they are wanted on the service
interphone and includes the following components: Also, the attendant call relay holds the call light on until reset with the RESET
switch on either attendant panel.
 the ATTEND CALL and
Pressing the ATTENDANT call switch on either attendant panel applies 28v DC
 GRD CALL switches and power to the green attendant call lights, to the attendant call relay, and to the
 the captain’s call light on the forward pilots’ overhead panel, chime in the PA amplifier.
 the ATTENDANT, CAPTAIN and RESET switches on the attendant The PA amplifier sounds a high-low chime through the PA system.
panels, Also, the attendant call relay holds the call lights on until reset with the RESET
 the PILOT CALL switch on the external power receptacle panel. switch on either attendant panel.
 the ground crew call horn, and The RESET switches on the attendant panels are connected in series.
 the attendant call lights on the exit locator signs. Thus, pressing one, removes power from the attendant relay and makes the
The call system gets power from the 28V DC bus No. 1 through the circuit call lights go off.
breaker on the P18 load control center.
Ground Crew Call
It is labeled PASS AND CREW CALL/LAV SMK DET or PASS AND CREW
Pressing the GRD CALL switch on the forward overhead panel P5 applies 28v
CALL on airplanes without lavatory smoke detectors.
DC power to the ground crew call horn.
OPERATIONAL USE The horn will sound as long as the switch is pressed.
The ground crew call horn also serves as an audible warning device for the IRS
Captain Call
FOR TRAINING PURPOSES ONLY!

(inertial reference system).

 Config. 1: The IRS warning system relay comes on in the flight instrument accessory unit
High Chime and Capts Call Light (blue) comes on, when a call from ground or integrated flight instrument accessory unit, and applies 28v DC power to the
personnel or from the attendants was initiated. ground crew call horn, whenever the IRS is powered by its battery or the IRS is
The Call Light goes out automatically after 40 seconds. turned on and the equipment cooling fan is not operating.
 Config. 2: The air−ground relay must be in the ground position before the IRS warning
High Chime and INT Call Lights on all ACPs come on, when a call from system relay can energize.
ground personnel on the external power panel was initiated.
High Chime and CAB Lights on all ACP’s come on, when a call from the
attendants is initiated.
Both lights go out automatically after about 40 s.

FRA US/T NM Nov 21, 2006 10/Call Sys/L2 Page 26

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
FLT/GRD CREW CALL SYSTEM
23−43

28V DC PASS CALL CAPTAIN

BUS NO. 1
PASS AND CREW
R380
CALL/LAV CALL RELAY
SMK DET ATTENDANT

TD
HI TONE
RESET
R392 TIME
CHIME DELAY RELAY
M315 AURAL WARNING MODULE
P14 AFT ATTENDANT’S PANEL
ATTEND
PILOT CALL
P P
P19 EXTERNAL POWER
CALL RECEPTACLE G G
B
L1086 EXIT L1088 EXIT
B LOCATOR SIGN LOCATOR SIGN
(STA 304) (STA 993)
MASTER
DIM AND
TEST TEST M53 GROUND
CREW HORN
L19 CALL LIGHT (STA 230)
RESET
FOR TRAINING PURPOSES ONLY!

GRD CALL R22

28V DC CREW CALL HORN
ATTENDANT’S
1 P6−1 ELECTRONIC CALL RELAY
P5 PILOTS’ FORWARD LOAD CB PANEL
OVERHEAD PANEL
M160 FLIGHT ATTENDANT
INSTRUMENT
ACCESSORY UNIT
(E1−2)
COMES ON WHEN IRS IS
1 POWERED BY ITS BATTERY, TWO TONE CAPTAIN
OR IRS IS ON AND EQUIPMENT CHIME
COOLING FAN IS NOT OPERATING.
M63 PA AMPLIFIER
(AIR−GROUND RELAY IS GROUNDED) (E2−1) P13 FORWARD ATTENDANT’S PANEL
Figure 15 Call System/Config. 1
FRA US/T NM Nov 21, 2006 10/Call Sys/L2 Page 27
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
FLT/GRD CREW CALL SYSTEM
23−43

THIS PAGE INTENTIONALLY LEFT BLANK

FOR TRAINING PURPOSES ONLY!

FRA US/T NM Nov 21, 2006 10/Call Sys/L2 Page 28

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
FLT/GRD CREW CALL SYSTEM
23−43

PASS CALL
TO INT
INT
28V DC CAPTAIN
CALL
BUS NO. 1 TD LIGHTS
PASS AND CREW ON ALL
CALL/LAV ACPs R380
TIME DELAY RELAY CALL RELAY
SMK DET R455(J5STAB. SHIELD
ATTENDANT

TD

HI TONE R392 TIME

RESET
DELAY RELAY
CHIME TO CABIN CALL
LIGHTS ON ALL
M315 AURAL WARNING ACPs P14 AFT ATTENDANT’S PANEL
MODULE
CABIN
ATTEND

PILOT CALL P P

P19 EXTERNAL POWER G G

RECEPTACLE
L1086 EXIT L1088 EXIT
LOCATOR SIGN LOCATOR SIGN
(STA 304) (STA 993)

M53 GROUND
CREW HORN
GRD CALL (STA 230)
FOR TRAINING PURPOSES ONLY!

RESET
28V DC CREW CALL HORN R22
ATTENDANT’S
1 P6−1 ELECTRONIC CALL RELAY
P5 PILOTS’ FORWARD
LOAD CB PANEL
OVERHEAD PANEL
M160 FLIGHT ATTENDANT
INSTRUMENT
ACCESSORY UNIT
(E1−2)
1
COMES ON WHEN IRS IS CAPTAIN
TWO TONE
POWERED BY ITS BATTERY,
OR IRS IS ON AND EQUIPMENT CHIME
COOLING FAN IS NOT OPERATING. M63 PA AMPLIFIER
(AIR−GROUND RELAY IS GROUNDED) (E2−1) P13 FORWARD ATTENDANT’S PANEL

Figure 16 Call Systems/Config. 2

FRA US/T NM Nov 21, 2006 10/Call Sys/L2 Page 29
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
FLT/GRD CREW CALL SYSTEM
23−43

CALL SYSTEM LOCATION OVERHEAD EXIT

LOCATOR SIGN
PANEL, P5

PILOTS’ CALL
SWITCHES

PA AMPLIFIER
(ELECTRONIC
LOAD CONTROL CHIME)
NO FASTEN AURAL WARNING CENTER, P18
SMOKING BELTS UNIT (CHIME)
OFF
CEILING
AUTO
(REF)
ON

GRD
FOR TRAINING PURPOSES ONLY!

ATTEND CALL

PAX CALL
ATTENDANT’S ATTENDANT’S LIGHT (BLUE) ATTENDANTS
LAVATORYCALL LIGHT
CALL LIGHT CALL LIGHT (AMBER)
CALL (PINK) (GREEN)
B
EXIT LOCATOR SIGN

PILOTS’ CALL SWITCHES

Figure 17 Call Systems/Component Location
FRA US/T NM Nov 21, 2006 11/CallSys LOC/L2 Page 30
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
FLT/GRD CREW CALL SYSTEM
23−43

EXIT
LOCATOR SIGN CALL SWITCHES
SEE (PREV. PAGE) CALL SYSTEM

CAPTAIN ATTENDANT RESET

LIGHTS
EXTERNAL INTERPHONE AFT BRT
POWER
ATTENDANT’S DIM
PANEL
OFF
ENTRY
CONN FLIGHT PARKING
SERVICE BRAKES AFT ATTENDANT’S PANEL
NOSE
PILOT WHEEL WELL FORWARD
ON LIGHTS
ATTENDANT’S BRT ON ON
NORM
CALL LIGHT
PANEL
NOT
IN USE DIM

OFF OFF OFF

ENTRY WORK GROUND
SERVICE
CALL SWITCH OFF DIM
BRT
EXTERNAL POWER RECEPTACLE NIGHT BRT

PANEL, P19 DIM

OFF
FIRST FIRST
CEILING WINDOW
FOR TRAINING PURPOSES ONLY!

OFF DIM
NIGHT BRT BRT

DIM

OFF
CALL SWITCHES TOURIST TOURIST
CEILING WINDOW
CALL SYSTEM

FORWARD ATTENDANT’S PANEL CAPTAIN ATTENDANT RESET

Figure 18 Call Systems/Component Location

FRA US/T NM Nov 21, 2006 11/CallSys LOC/L2 Page 31
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

23−31 PASSENGER ADDRESS

PASSENGER ADDRESS- INTRODUCTION
Purpose General
The PA (Passenger Address) system supplies these to the passenger cabin: The PA amplifier puts a priority on the audio inputs from these places:
 Passenger address announcements  Pilots
 Pre−recorded announcements  Attendants
 Boarding music  Pre−recorded announcement and boarding music tape reproducer
 Chimes The PA amplifier amplifies the audio input that has the highest priority and
sends the signal to these places:
Abbreviations and Acronyms
 Passenger cabin speakers
ACP Audio Control Panel
 Attendant speakers
AMP AMPlifier
 REU (Remote Electronics Unit)
ATT ATTendant
The amplified audio to the REU goes through muting circuits for the forward
ATTD ATTenDant
and aft attendant speakers.
BGM BoardinG Music
When an attendant makes an announcement, the muting circuits stop the
BITE Built−In Test Equipment audio for that attendants speaker.
DB DeciBel The PA amplifier supplies chimes with other PA audio.
DECOMPR DECOMPRession
EEC Electronic Equipment Compartment
fwd ForWarD
IND INDication
LCD Liquid Crystal Display
LED Light Emitting Diode
FOR TRAINING PURPOSES ONLY!

MIC MICrophone
OXY OXYgen
PA Passenger Address
PRAM Pre−Recorded Announcement and boarding Music reproducer
PTT Push To Talk
REPR REPRoducer
REU Remote Electronics Unit
SSSV Solid State Stored Voice

FRA US/T NM Sep 15, 2006 12/PA INTRO/23−31/L1 Page 32

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

AAU OBS F/O CAPT

SVR INT
SVR INT
EXT
ATT
ATT
HDPHSPKR
FLT
HDPH
FLT
FLT INT
ONE 2
MUTING-RELAIS
ADJ
SVR SVR
ATT SPEAKERS
DME 1 ADJ
PA SENS
PA GAIN
PA ST ATTENTION
AUDIO POT 1 ELECTROSTATIC
AUDIO POT 2 SENSITIVE
DEVICES COLLINS
MOD A[] B[] C[] D[]
FLIGHT DECK −1 0 db +1
REMOTE ELEC ONICS UNIT
CABIN AND
RVTECH P/N LAV SPEAKERS
BOEING P/N
TSO C50C NORM
RTCA 00−16 ENV CAT TEST CAL
B2AKXXXXFX AAZ

SERIAL NO.
DATE MFD
WEIGHT 7.75 LBS

REMOTE ELECTRONIC UNIT

ATTENDANT

NO FASTEN
SMOKING BELTS
OFF
AUTO
FOR TRAINING PURPOSES ONLY!

MUSIC

1 2 3 ON
READY
4 5 6

7 8 9
START STOP GRD
0 1 2 ATTEND CALL
PAX-CALL

LAVATORIES
ANNOUNCEMENT/ AND PASS PASSENGER SIGNS
MUSIC REPRODUCER SERVICE UNITS PANEL
PASSENGER ADDRESS AMPLIFIER
Figure 19 PA-General Description
FRA US/T NM Sep 15, 2006 12/PA INTRO/23−31/L1 Page 33
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

PA-SYSTEMARCHITECTURE
Power Gain Control
The passenger address (PA) amplifier gets 28V DC from the 28V DC battery The PA amplifier receives gain-adjustment signals from the REU.
bus. The REU receives inputs from the engine oilpressure switch-relays.
Audio When the engines operate, the PA amplifier gain increases to compensate for
the increase in the ambient noise level.
The PA system receives audio from these sources:
 Flight compartment microphones Training information point
 Attendant microphones. At the front of the REU are adjustments for the passenger address system.
The pre−recorded announcement and boarding music tape reproducer also Check your airlines procedures if adjustments are allowed for line maintenance
supplies audio to the PA system. personal or not.
 Flight compartment audio has the first priority. If passenger oxygen system is ON, the tape reproducer starts solid state
 The second priority is from the attendant microphones. memory stored emergency announcements.
 The third priority is pre−recorded announcements.
 The fourth priority is boarding music.
Priority circuits in the PA amplifier receive the audio inputs and set their priority.
The audio with the highest priority is amplified and goes to the speakers.
The PA amplifier supplies the side tone to the remote electronics unit (REU).
The REU supplies the side tone to the flight crew headsets.
The PA amplifier supplies audio to these components and system:
 REU, for the attendants speaker mute relays
 Passenger and lavatory speakers
The REU supplies audio to the attendant speakers.
FOR TRAINING PURPOSES ONLY!

Chimes
The PA amplifier supplies chimes for these conditions:
 Lavatory smoke − high chime
 NO SMOKING/FASTEN SEAT BELTS signs operate − low chime
 Attendant call − high chime from passenger service units and lavatories,
high/low chime from the flight compartment and attendant stations.

FRA US/T NM Sep 15, 2006 13/INTERF/23−31/L2 Page 34

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

28V DC
BAT BUS POWER
PA AMP BAT A B C D
P6 CIRCUIT BREAKER PANEL

MIKE AUDIO A INPUT 1

PTT 1 B PTT 1
PTT 2
FLT INTERPHONE SYSTEM
SIDE TONE FLIGHT CREW
MIC AUDIO INPUT 2
PTT 2 C PA
ATTENDANT CALL HIGH/LOW CHIME GAIN
LEVEL ADJUST
PILOT/ATT CALL
AUDIO MUTING ATTENDANT
FWD ATTENDANT PANEL FUNCTIONS: OUT RELAYS SPEAKERS
AMPLIFIER GAIN GAIN
ATTENDANT CALL CONTROL
MIC AUDIO
PRIORITIES
PTT 2 D REU
OXYGEN ON
AFT ATTENDANT PANEL CHIME
OIL OIL
115V AC PTT −1 0 db +1 PRESS PRESS
BOARDING MUSIC INPUT 4 SW
XFR BUS−2 NORM SW
ANNOUNCEMENTS TEST CAL
TAPE RPDR INPUT 3
PTT ENGINE 1 ENGINE 2
P6 CIRCUIT BREAKER
PANEL TAPE REPRODUCER
FOR TRAINING PURPOSES ONLY!

PASSENGER LOW CHIME

FASTEN SEATBELT
SIGNS NO-SMOKING LOW CHIME
PANEL P5

PASSENGER SERVICE UNITS

SMOKE DETECTOR HIGH CHIME
ATTENDANT CALL HIGH CHIME AND LAVATORY SPEAKERS

LAVATORIES ANDPASSENGER SERVICE UNITS PASSENGER ADDRESSAMPLIFIER

Figure 20 PA-System Architecture

FRA US/T NM Sep 15, 2006 13/INTERF/23−31/L2 Page 35
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

PA COMPONENTS - LOCATION

PSU SPEAKER
(EXAMPLE)
−1 0 db +1
LOAD CONTROL
CENTER, P6 NORM
TEST CAL

PA AMPLIFIER
(E2−1)

ELECTRONIC
EQUIPMENT
REMOTE RACK, E2
ELECTRONIC
UNIT (E2−1)
FOR TRAINING PURPOSES ONLY!

SELECTOR PA AMPLIFIER
FLIGHT
− 2 INT PA
HF − 2 PA CREW
PA MIC
SELECTOR

REMOTE ELECTRONICS UNIT

AUDIO CONTROL PANEL
Figure 21 PA - Component Location 1
FRA US/T NM Sep 15, 2006 14/PA LOC Comp/L2 Page 36
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

AFT ATTENDANT’S SEE NEXT PAGE

SPEAKERS FOR SPEAKERS
(LOWERED CEILING)

FORWARD
ATTENDANT’S
SPEAKER
FORWARD (LOWERED CEILING)
ATTENDANT
STATION

CALL SYSTEM MICROPHONE ON AFT

ATTENDANT’S PANEL
CAPT ATTD RESET

ATTENDANT TAPE REPRODUCER

PA LEFT GALLEY WALL
MICROPHONE

MUSIC

1 2 3
4 5 6 READY

7 8 9 START STOP
0 1 2
FOR TRAINING PURPOSES ONLY!

FORWARD ATTENDANT’S PANEL TAPE REPRODUCER AFT ATTENDANT’S PANEL

Figure 22 PA - Component Location 2
FRA US/T NM Sep 15, 2006 14/PA LOC Comp/L2 Page 37
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

PASSENGER ADDRESS SYSTEM - SPEAKERS

Features
Each passenger service unit (PSU) has a 6.5 inch speaker.
There is a 5 inch speaker in each lavatory and at the attendant stations.
The attendant station speakers connect through mute relays in the remote
electronics unit.
The mute relays prevent the attendant speaker from operating during PA
announcements. This prevents feedback through the speakers.
To open the assembly, you will put a small rod in the access holes.
You will hold the PSU panel, and push the rod against the spring clips to open
the assembly.
Each speaker has a transformer.
The transformer matches the speaker impedance to the line impedance and
steps down the operating voltage from appr. 70 V AC to appr. 2−3 V AC.
Two electrical wires connect the speaker transformer terminals to the PA
amplifier.
Install and remove the speaker and transformer as one assembly.

Training Information Point

When you remove the electrical wires from the speaker transformer terminals,
make sure to record the terminal connections.
When you replace the speakers, you will put the electrical wires to the same
terminals.
When you remove the speaker from the PSU assembly, make sure you do not
damage the speaker gasket.
FOR TRAINING PURPOSES ONLY!

This gasket is between the speaker and the PSU assembly.

FRA US/T NM Sep 15, 2006 14/PA LOC Comp/L2 Page 38

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

PSU ACCESS HOLES IMPEDANCEMATCHING

TRANSFORMER RETENTION
LANYARD
SPEAKER

ELECTRICAL
CONNECTORS
FWD GASKET TRANSFORMER
(UNDER
SPEAKER)

WIRING LATCH
ELECTRICAL
CABIN SPEAKER (TYPICAL)
LAVATORY SPEAKER (TYPICAL)

SPEAKER DOOR HEADER ELECTRICAL

CONNECTORS (2)
PANEL
TRANSFORMER
FOR TRAINING PURPOSES ONLY!

ATTENDANT
SPEAKER

FWD
ATTENDANT STATION (TYPICAL) DOOR HEADER PANEL (OPEN) LAVATORY (TYPICAL)

Figure 23 PA-Speakers Locations

FRA US/T NM Sep 15, 2006 14/PA LOC Comp/L2 Page 39
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

TAPE REPRODUCER
GENERAL
The tape reproducer is operated from the controls on the face of the unit. It will play automatically and repeat upon closing of the OXY IND relay, R324.
There are controls for selection and play of both boarding music and This relay closes as part of the sequence during activation of passenger
prerecorded announcements. oxygen.
To open the door holding the tape magazine, display 90 in the window and All keyboard, START, STOP, and channel 1 or 2 buttons backlight when
press music channel switches 1 and 2 simultaneously. pushed.
MUSIC The channel selection 1 and 2 buttons are push−on/push−off.
The front face of the tape reproducer has MUSIC controls for off/on/volume All other buttons are momentary.
and selection of music channel 1 or 2. All the programs are on one C−60/90 Phillips four channel cassette tape.
To playback boarding music program 1 or 2, press MUSIC channel button 1 or Two of the channels are for boarding music; one for selected announcements.
2 and press the START button.
Adjust music volume by rotating MUSIC control. EMERGENCY ANNOUNCEMENTS
Either music program may be stopped at any time by pressing the STOP The emergency announcements are stored on a SSSV
button. (Solid State Source Voice) .
The boarding music program being played may also be switched at any time by They are automatically started with passenger oxygen masks deployed or by a
pressing the other MUSIC channel button. code entered on the tape reproducer.
To start the emergency announcements:
PRERECORDED ANNOUNCEMENT
 press STOP,
The front face of the reproducer has the controls for selecting and playing
 enter code 89,
prerecorded announcements.
 press music track 1 and 2 simultaneously
The selection is made with a numerical keyboard which selects the desired
announcement by number and displays the selection in the window. and the emergency announcement will start.
Upon selecting an announcement, boarding music will cease and the Tape access
reproducer will search for and key at the start of the selected announcement.
To get access to the tape (open casette-door):
FOR TRAINING PURPOSES ONLY!

The READY light indicates the completion of the search mode.

 press STOP,
Pushing the START button will initiate playing of the announcement.
 enter code 90,
If START is pressed before the search is complete the search will continue and
 press music track 1 and 2 simultaneously
announcement playback will start immediately upon completion of search.
and the door will open.
The announcement will play to completion or until STOP is pressed, after which
time the reproducer will return to the boarding music mode of operation before To open the casette-door without power:
announcement selection. In the right hand slot between door and housing, insert a small blade (ID-card)
An oxygen emergency announcement has priority over any other in an tilted down attitude and lift it thus you can lift the mechanical lock and the
announcement or boarding music. This announcement is not manually door opens springloaded.
selected.

FRA US/T NM Sep 15, 2006 15/PA Tape−Repr/L2 Page 40

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

ANNOUNCEMENT
TRACK DISPLAY

MESSAGE
ADDRESSING READY LAMP
MUSIC
KEYBOARD
1 2 3 MUSIC
4 5 6 READY VOLUME
CONTROL
7 8 9 START STOP

0 1 2

MUSIC
TRACK S1−1
SELECT S1−2
START-STOP TAPE DOOR
S1−3
CONTROLS LOCK
S1−4
LIST OF PRE-RECORDED ANNOUNCEMENTS
1 . ENGLISH S1−5 BUTTON
2. GERMAN BEEP
S2−1
3. SPAIN
FOR TRAINING PURPOSES ONLY!

4. ........ S2−2 EMERGENCY

S2−3
MESSAGE
PLAYBACK
S2−4 TIMES

BEHIND COVER:
DIP_SWITCHES FOR
CUSTOMIZED SETTINGS

Figure 24 PA/Tape Reproducer

FRA US/T NM Sep 15, 2006 15/PA Tape−Repr/L2 Page 41
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

PA-AMPLIFIER/TEST
AMPLIFIER VERSION 346D-2B
The self−test switch on the PA amplifier front panel provides tests of the
operation status of the PA system.

CAL Position
The spring loaded CAL position applies the amplifier output to an internal load.
The power applied is displayed on the LED indicators.
Make sure that the -1 and the 0 dB LED’s on the PA amplifier come on.
If the -1 and the 0 dB LED’s do not come on, adjust the MASTER GAIN
potentiometer until this both LED’s come on.
The MASTER GAIN potentiometer is on the lower part of the front panel on the
PA amplifier.

Test Position
The TEST position supplies a high chime sound to all speakers.
Make sure you hear a high chime sound on all the PA speakers.

AMPLIFIER VERSION 346D-1B

CAL Position
Setting in CAL position the testmeter indicates 0 dB.

Test Position
Setting in TEST TONE position a calibrated tone is applied to the input of the
amplifier and applied to all speakers.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Nov 21, 2006 17/PA Test/L2 Page 42

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
PASSENGER ADDRESS
23−31

COLLINS

-1 0 db +1

NORM
TEST CAL
FOR TRAINING PURPOSES ONLY!

PA AMPLIFIER PA AMPLIFIER
346D−2B AMPLIFIER 346D -1B AMPLIFIER
Figure 25 PA Amplifier
FRA US/T NM Nov 21, 2006 17/PA Test/L2 Page 43
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF-COMMUNICATION
23−21

23−21 VERY HIGH FREQUENCY SYSTEM

INTRODUCTION
The very high frequency (VHF) communication system supplies voice and data External Interface
communication over line−of−sight distances. It gives communication between The VHF communication system connects with these components/systems:
airplanes or between ground stations and airplanes.
 The flight interphone system via the remote electronics unit (REU) (not
The VHF system operates in the aeronautical frequency range of 118.000 MHz shown in this diagram)
to 136.975 MHz.
 The flight data acquisition unit (FDAU)
VHF - GENERAL DESCRIPTION: CONFIG 1 Microphone audio and microphone discretes go to the VHF transceiver through
the remote electronics unit.
General
Receiver audio goes from the VHF transceiver to the flight interphone speakers
The VHF communication system supplies the flight crew with voice and data and headsets through the remote electronics unit.
line-of-sight communication.
The flight data acquisition unit receives transceiver key data to record the
The VHF communication system can be used to communicate between event.
airplanes and between airplanes and ground stations.
The VHF communication radio is tunable in the frequency range of 118.000
MHz to 136.975 MHz.
The channel spacing is 8.33 kHz.

System Components
Each VHF communication radio has these components:
 Radio Communication Panel for VHF frequency control
 VHF transceiver
 VHF antenna
The aircraft communication and reporting system (ACARS) uses the VHF 3
FOR TRAINING PURPOSES ONLY!

transceiver to transmit data.

It also may be used for voice communications.

FRA US/T NM Sep 21, 2006 01/VHF GEN/L1 Page 44

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF-COMMUNICATION
23−21

118 , 000 136 , 975 SOL/LAMP

TEST OFF

REF FWD
ACTIVE STANDBY CONTROL
INPUT LRU
PASS
TO
VHF 1 VHF 3 VHF 2
FAIL

PHONE MIC
FDAU

O
FLIGHT INTERPHONE VHF−700B TEST

F OFF
F
MICROPHONES
RADIO COMMUNICATION HEADPHONES
PANEL 1 OXYGEN MASKS
SPEAKERS VHF 1 TRANSCEIVER

COLLINS

LRU

CONTROL

ACARS 136 , 975 ANTENNA

TO
ACTIVE STANDBY PHONE
FDAU
VHF 1 VHF 3 VHF 2 MK II
TUNE MIC

VHF−900

MU PASS
O
HW FAIL
F OFF CMU LOAD SW

F XFER
BUSY
XFER
COMP
XFER

RADIO COMMUNICATION FAIL

APM
FAIL

PANEL 3 VHF 3TRANSCEIVER

LIFT
SLIDE
FOR TRAINING PURPOSES ONLY!

SOL/LAMP
TEST OFF

118 , 000 136 , 975 ACARS MU

CONTROL
INPUT
REF

LRU
FWD

TO
FAIL PASS

ACTIVE STANDBY PHONE MIC

FDAU
VHF 1 VHF 3 VHF 2 VHF−700B TEST

O
F OFF
F

RADIO COMMUNICATION PANEL 2 VHF 2 TRANSCEIVER

Figure 26 VHF-General Description, Conf. 1
FRA US/T NM Sep 21, 2006 01/VHF GEN/L1 Page 45
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF-COMMUNICATION
23−21
VHF - GENERAL DESCRIPTION: CONFIG 2
General
The VHF communication system supplies the flight crew with voice and data
line-of-sight communication.
The VHF communication system can be used to communicate between
airplanes and between airplanes and ground stations.
The VHF communication radio is tunable in the frequency range of 118.000
MHz to 136.975 MHz.
The channel spacing is 8.33 kHz.

System Components
Each VHF communication radio has these components:
 VHF frequency control panel
 VHF transceiver
 VHF antenna
VHF 3 transceiver is only for the aircraft communication and reporting system
(ACARS) to transmit data.
In configuration 2, the VHF 3 cannot be used for voice communications as in
configuration 1.

External Interface
The VHF communication system connects with these components/systems:
 The remote electronics unit (REU)
 The flight data acquisition unit (FDAU)
Microphone audio and microphone discretes go to the VHF transceiver through
FOR TRAINING PURPOSES ONLY!

the remote electronics unit.

Receiver audio goes from the VHF transceiver to the flight interphone speakers
and headsets through the remote electronics unit.
The flight data acquisition unit receives transceiver key data to record the
event.

FRA US/T NM Sep 21, 2006 01/VHF GEN/L1 Page 46

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF-COMMUNICATION
23−21

ACTIVE TFR STANDBY

V C SOL/LAMP
H O TEST OFF
F M REF FWD
M CONTROL
INPUT LRU
FAIL PASS VHF ANTENNA
PHONE MIC
VHF CONTROL PANEL CAPTAIN
TEST
VHF−700B
DO NOT
ADJUST
1−VHF

FLIGHT INTERPHONE AUDIO CONTROL PANEL FLIGHT DATA

ACQUISITION UNIT
MICROPHONES
HEADPHONES VHF TRANSCEIVER 1
REMOTE ELEC ONICS UNIT
OXYGEN MASKS RVTECH P/N
SPEAKERS BOEING P/N
TSO C50C
RTCA 00−16 ENV CAT
B2AKXXXXFX AAZ

1−VHF 2−VHF
SOL/LAMP
TEST OFF
AUDIO CONTROL PANEL SERIAL NO.
DATE MFD REF FWD
CONTROL
FOR TRAINING PURPOSES ONLY!

WEIGHT 7.75 LBS

INPUT LRU
FAIL PASS VHF ANTENNA
REMOTE ELECTRONICS UNIT
ACTIVE TFR STANDBY PHONE MIC

V C VHF−700B
TEST
H O
F M
M

FLIGHT DATA
VHF CONTROL PANEL FIRST OFFICER VHF TRANSCEIVER 2 ACQUISITION UNIT
Figure 27 VHF - General Description Conf. 2
FRA US/T NM Sep 21, 2006 01/VHF GEN/L1 Page 47
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
SPEECH COMMUNICATION
23−10

23−10 SPEECH COMMUNICATION

RADIO COMMUNICATION PANEL
The radio communication panels RCP-1, RCP-2 and RCP-3 are installed on SYSTEM FUNCTION
the aft electronics panel, P8. The frequency selected will show in the STANDBY frequency display and can
Each RCP can make a radio selection and a frequency selection for each of be transferred to the ACTIVE frequency display by action of the transfer switch.
available radio systems. Then another STANDBY frequency selection can be made.
To set the RCP for a VHF system, push the applicable radio selector switch on This pair of frequencies is monitored by all RCP’s.
the RCP (VHF-1, VHF-2 or VHF-3).
All RCP’s are connected via a cross-bus and to the associated transceiver.
The switch light will come on to show the selection was made at that RCP.
Whenever this radio is called up on another RCP, the frequency pair originally
Use the frequency selector knobs, frequency displays and an selected with the on-side RCP will then show on the off-side RCP.
ACTIVE/STANDBY transfer switch to set the RCP for a frequency selection.
The OFF SIDE CONTROL light will illuminate on both RCP’s.
Each RCP has an ACTIVE frequency display and a STANDBY frequency
When a failure occurs the indication FAIL appears in the ACTIVE display
display.
window.
The ACTIVE frequency display shows the frequency to which the selected
In this case the onside transceiver can not be tuned from the associated RCP.
radio is tuned.
With the OFF switch you must disable this RCP.
The OFF switch disables the RCP. This is only intended to used in the event of
Than the transceiver can be tuned from other RCP’s.
RCP failure.
The third VHF transceiver is originally connected with the ACARS management
All radios can still be controlled from other RCP’s in the event of a single RCP
unit. The VHF-3 is used by the ACARS to transmit and receive messages.
failure.
When you select the VHF-3 transceiver on a RCP, the message DATA or
The OFF SIDE CONTROL light illuminates whenever an RCP is used to select
ACARS (depending on customer option) appears in the ACTIVE frequency
a frequency for an OFF-SIDE radio (refer to the operation paragraphs for a
window on this RCP.
definition of OFF-SIDE).
Radio normally associated with this VHF panel is being tuned by another VHF
panel.
FOR TRAINING PURPOSES ONLY!

For the onside transceiver:

 Left RCP is normally associated with VHF-1
 Right RCP is normally associated with VHF-2
 Center RCP is normally associated with VHF-3 (ACARS - MU)

FRA US/T NM Sep 21, 2006 02/RCP/L2 Page 48

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
SPEECH COMMUNICATION
23−10

OFF MODE

ACTIVE FREQUENCY OFF-SIDE CONTROL LIGHT

ACTIVE STANDBY
TRANSFER SWITCH STANDBY FREQUENCY RCP BITE PASSES

DISPLAY WITH VHF 1 / 2 SELECTED

118.000 136.975 118.000 136.975

ACTIVE STANDBY STANDBY
ACTIVE
VHF 1 VHF 3 VHF 2
DISPLAY WITH VHF 3 SELECTED
O
F OFF
F DATA 118.000
ACTIVE STANDBY
THE DISPLAY ABOVE ONLY MAY APPEAR IF ACARS IS
ACTIVE AND VHF 3 WAS SELECTED ON A RCP.
THE ACTIVE DISPLAY MAY SHOW „ACARS“ OR „DATA“.
THIS DEPENDS OF CUSTOMER OPTION SELECTED.
VHF RADIO SELECTORS
FOR TRAINING PURPOSES ONLY!

PANEL-OFF SWITCH FREQUENCY SELECTORS

DISPLAY FOR FAIL MODE (WITH RCP ON - OR - OFF)
RADIO COMMUNICATION PANEL (RCP)
INOP INOP
ACTIVE STANDBY
CUSTOMER OPTION:
DISPLAYS ALSO COULD SHOW FAIL IN BOTH WINDOWS.
Figure 28 Radio Communication Panel
FRA US/T NM Sep 21, 2006 02/RCP/L2 Page 49
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF - COMMUNICATION
23−21

23−21 VHF-COMMUNICATION
SYSTEM DESCRIPTION
General An off-side condition will turn on the cross-tuning annunciator on the RCP-1
The very high frequency (VHF) communication system provides short-range and RCP-2 and will activate tuning port B of the selected off-side radio.
two-way voice and data communication in the frequency range of 118.000 The off-side RCP will acquire the tuning selections from the on-side radio and
through 136.975 MHz with a RF power of about 25 W (AM) . will tune the off-side radio with the ACTIVE frequency acquired from the
Three VHF systems are installed in the airplane. on-side RCP through tuning port B of the off-side transceiver.
The communication equipment for each VHF system includes a VHF Tuning port A for VHF−3 is reserved for future ACARS input. VHF−3 is tuned
transceiver, a RCP and a blade antenna. only through tuning port B.
Each VHF system interfaces with the audio integration system and the Selecting VHF−3 from any RCP, other than RCP−3 will result in off−side
SELCAL system. operation.
VHF-1 system power is obtained from the hot battery bus, VHF-2 system Thus, the radio controlled from the off-side RCP will keep the same frequency
power is obtained from switched electronics bus No. 2 and VHF-3 system but will be tuned through port B.
power is obtained from DC bus No. 1. Tuning port A for VHF-3 is reserved for the ACARS input, VHF-3 is tuned only
through tuning port B.
OPERATION (VHF - 700 COLLINS)
Port Select
Description
Port Select means input-select. It is used in many systems like
The VHF system consists of: VHF-transceiver.
 transceiver Collins VHF-700 (E2-1) With port-select discrete available, the input selector contacts to input A.
 radio control panel (P8) With port-select discrete not available, the input reverts to input B.
 blade antenna
The frequency selection data originates in the RCP is transmitted to the
transceiver over an ARINC 429 data bus.
INPUT A
FOR TRAINING PURPOSES ONLY!

Each VHF transceiver has two ports (A and B) for receiving tuning data. TO MICROPROCESSOR
(INTERNAL OF THE UNIT)
The VHF No.1 transceiver receives the tuning data from the ACTIVE frequency INPUT B
on RCP-1 through port A when VHF-1 is selected on RCP-1.
Similarly the VHF No.2 transceiver receives the tuning data of the ACTIVE PORT
frequency on RCP-2 through port A when VHF-2 is selected on RCP-2. SEL.
This operation is on-side operation. INPUT SELECTOR
The VHF transceiver A tuning ports are active and the cross-tuning
annunciators are off.
LRU (VHF-TRANSCEIVER)
The selection of any VHF except No.1 by RCP-1, or the selection of any VHF
radio except No.2 by RCP-2, constitutes an off-side condition.

FRA US/T NM Sep 21, 2006 03/VHF Sys/L2 Page 50

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF - COMMUNICATION
23−21

VHF−1
28V DC 1

STANDBY BUS PORT SELECT SOL/LAMP

TEST OFF

P18−2 CIRCUIT BR. PNL. TUNE PORT A REF FWD

CONTROL
INPUT LRU
PASS
TO
FAIL

PHONE MIC
FDAU
120 000 12115 0 PORT B
ACTIVE STANDBY VHF−700B TEST

VHF VHF
1 VHF
3 2 CROSSTALK 1
O
F
F OFF

RADIO COMMUNICATION CROSSTALK 2

PANEL 1 VHF1 TRANSCEIVER

VHF−3 COLLINS

28V DC 3 3 LRU

ELECTRONICS BUS 1 CONTROL

ANTENNA
P18−2 CIRCUIT BR. PNL.
TUNE TO
DATA 12115 0
PHONE
FDAU
PORT B
ACTIVE STANDBY CROSSTALK 1 MK TUNE
II MIC
VHF VHF
1 VHF
3 2
PORT A VHF−900

MU PASS
O
F
F OFF DATA HW FAIL
PORT SELECT
CMU LOAD SW

RADIO COMMUNICATION CROSSTALK 2

XFER
BUSY
XFER
COMP

PANEL 3 XFER
FAIL
APM
FAIL

VHF3 TRANSCEIVER

LIFT
VHF−2 SLIDE

28V DC 2
FOR TRAINING PURPOSES ONLY!

ELECTRONICS BUS 2
2 1

P6−1 CIRCUIT BR. PNL. CROSSTALK 1 SOL/LAMP

TEST OFF

ACARS MU REF FWD

120 000 12115 0 CROSSTALK 2

CONTROL
INPUT
FAIL
LRU
PASS
TO
ACTIVE STANDBY PHONE MIC
FDAU
VHF VHF
1 VHF
3 2 PORT SELECT
O VHF−700B TEST
F
F OFF
TUNE PORT A
RADIO COMMUNICATION
PANEL 2 PORT B
VHF2 TRANSCEIVER
Figure 29 VHF-700 Collins System Architecture
FRA US/T NM Sep 21, 2006 03/VHF Sys/L2 Page 51
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF - COMMUNICATION
23−21

VHF SYSTEM - LOCATION

VHF 1 ANTENNA

VHF 2 ANTENNA VHF 3 ANTENNA

FOR TRAINING PURPOSES ONLY!

Figure 30 VHF - Antenna Locations

FRA US/T NM Sep 21, 2006 04/VHF LOC/L2 Page 52
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF - COMMUNICATION
23−21

VHF−2 POWER, LOAD

CONTROL CENTER, P6

RADIO COMMUNICATION
PANELS NO. 1,2,3,
AFT ELECTRONIC
PANEL, P8 ELECTRONIC
EQUIPMENT
RACK, E2

SQL/LAMP
VHF−1,−2,−3 TEST OFF
TRANSCEIVERS
RFL FWD

CONTROL LRU
VHF−1 AND VHF−3 POWER, INPUT PASS
FAIL
LOAD CONTROL CENTER, P18
PHONE
MIC

VHF−700 TEST
FOR TRAINING PURPOSES ONLY!

ACTIVE STANDBY

VHF1 VHF3 VHF2

OFF

VHF TRANSCEIVER
RADIO COMMUNICATION PANEL
Figure 31 VHF 700 Collins Locations
FRA US/T NM Sep 21, 2006 04/VHF LOC/L2 Page 53
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF - COMMUNICATION
23−21

VHF 700 / 900 - BITE DESCRIPTION

Squelch/Lamp−Test−Switch
This test switch is used to disable the squelch (you can hear a noise sound)
and to check the front panel lights prior to system self-testing.
VSWR/
The red CONTROL INPUT FAIL and the green LRU PASS lights come on POWER
when this test switch is pushed. DISPLAY
Test−Switch
The CONTROL INPUT FAIL test checks that the VHF transceiver is receiving
valid frequency tuning data from the VHF control panel RCP.
SQL/LAMP
If the tuning data is not valid, the red CONTROL INPUT FAIL light comes on TEST SQL/LAMP
indicating a VHF control panel failure. SWITCH TEST OFF
This light remains on for about four seconds after TEST switch is pressed.
RFL FWD
The LRU PASS test identifies a failure on the VHF transceiver.
After pressing the TEST switch, the green LRU PASS should light for
CONTROL LRU
approximately one to four seconds. HEADPHONE INPUT PASS RFL/OFF/FWD
At the same time, the digital display should show a value of less than 3.0. FAIL
(PHONE) POWER TEST
This value is the voltage standing wave ratio (VSWR) .
JACK SWITCH
PHONE MIC
RFL−OFF−FWD Switch
After the CONTROL INPUT FAIL / LRU PASS tests are completed, turning the TEST RESULT
power test switch to FWD or RFL displays the forward or reflected power LEDs
values on the digital display. VHF−700 TEST
The FWD position should display a minimum value of 25 (that means 25 W). MICROPHONE
The RFL position should display about 25 percent or less of the forward power (MIC) JACK
FOR TRAINING PURPOSES ONLY!

value.
ATTENTION: The Figure on the right shows the VHF 700 transceiver whereas TEST
the figure on the next page shows the VHF 900 transceiver. SWITCH

VHF 700 - TRANSCEIVER

FRA US/T NM Sep 21, 2006 06/VHF BITE/L2 Page 54

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
VHF - COMMUNICATION
23−21

COLLINS
TIME, TEST INDICATION
AFTER TEST LRU CONTROL ANTENNA TEST
STARTS STATUS FAIL FAIL RESULT
LRU STATUS
0−3
ON−RED ON−RED ON−RED −
CONTROL FAIL SECONDS

ANTENNA FAIL 3−6

ON−GREEN ON−RED ON−RED −
SECONDS

6−9
OFF OFF OFF −
SECONDS
PHONE TEST
9−39
ON−GREEN OFF OFF PASS
SECONDS

MIC
XCVR
ON−RED OFF OFF FAULT
VHF−900
CONTROL
ON−GREEN ON−RED OFF PANEL
FOR TRAINING PURPOSES ONLY!

FAULT
ANTENNA
ON−GREEN OFF ON−RED SYSTEM
FAULT

39+
OFF OFF OFF −
SECONDS

VHF 900 - TRANSCEIVER

Figure 32 VHF 900 - TRANSCEIVER BITE
FRA US/T NM Sep 21, 2006 06/VHF BITE/L2 Page 55
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

23−11 HF-COMMUNICATION
HF SYSTEM - DESCRIPTION HF Transceiver
Each transceiver is a tray−type unit located in the electronic equipment rack,
A single HF (High Frequency) communication system is installed in the
shelf No. E6−2. Electrical connection is made through connector located at the
airplane. The HF communication system (referred to as the HF system)
rear of the HF transceiver also the Antenna line connection. An internal blower
provides amplitude modulated and single sideband voice communication
provides forced air cooling for the HF transceiver components. The blower is
between airplane and ground or other airplanes.
located towards the rear of the HF transceiver and operates during
Communication is in the 2.000 to 29.999 MHz frequency range on any of
transmission cycles.
28,000 channels at 1 kHz spacing. Propagation characteristics of the HF band
are most suitable for long distance communications. Each HF transceiver panel contains:
The HF system is composed of a control panel, a transceiver, an antenna 1. LRU FAIL light that comes on as a result of HF transceiver faults.
coupler and an HF antenna. 2. KEY INTERLOCK light that is activated as a result of HF antenna coupler
The control panel is installed on the aft electronics control stand. faults.
The HF transceiver and adapter is installed on electronic equipment rack E6.
3. CONTROL INPUT FAIL light that is activated as a result of control faults.
The flush−mounted HF antenna is part of the vertical fin leading edge.
The HF antenna coupler is installed inside the vertical fin leading edge 4. SQL/LAMP TEST switch which tests the above indicator lights and disables
approximately under the HF antenna. squelch of receiver audio.
The control panel enables the desired communication channel to be selected. 5. PHONE jack, a 600−ohm headset plug−in to monitor test audio.
Sidetone is connected to the HF system audio switch in the flight interphone 6. MIC jack, to enable voice modulation for tests at the HF transceiver.
system.
The HF antenna coupler matches the characteristic antenna impedance to the HF Antenna
impedance of the HF transceiver at the particular frequency on which the The HF system transmits and receives thru a flush−mounted shunt−fed slot
system is operating. The tuner control unit and tuner will automatically keep the type of antenna which is located in the vertical fin leading edge.
voltage standing wave ratio (VSWR) to a level between 1.3 and 1.0 thus The HF antenna is the metal leading edge of the vertical fin and its dielectric
assuring good power transfer. Communications are completed through the portion is constructed of fiberglass.
flight interphone system The HF system uses 3−phase, 115−volt, 400−Hz AC
power obtained from load control center P18. HF Antenna Coupler
An HF antenna coupler is located just below the HF antenna in the vertical fin
FOR TRAINING PURPOSES ONLY!

Control Panel
leading edge. Electrical connection is provided through a connector located
The control panel can select any one of 28,000 channels, spaced 1 kHz apart on the unit front. The RF connection is through a coaxial plug designated RF
in the 2.000 to 29.999 MHz range. INPUT and is also located on the front panel whereas the antenna connection
It contains four frequency select knobs, a frequency display, SQ (SQuelch) is on the unit rear panel.
knob and a mode select switch. The SQ knob controls audio gain in the The pressurized case has two sections divided by an RF shield which provides
receiving section of the HF transceiver. thermal protection and RF isolation.
The mode select switch turns the system off (OFF) , selects upper sideband The forward compartment contains tuning control modules, the rear section of
(USB) , and amplitude modulation (AM) . the HF antenna coupler (the RF compartment) contains the tuning elements.
A ten position rotary switch controls the calsel system) . The tuning elements consist of two variable vacuum capacitors and a variable
inductor, associated motors, gear trains, switches, and RF relays.

FRA US/T NM Sep 13, 2006 07/HF Sys/L2 Page 56

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

M889 RF
FEEDLINE
M228 HF
TO SELCAL LEADING EDGE
SYSTEM SLOT ANTENNA
COLLINS
PTT FROM AUDIO
SQL/LAMP TEST INTEGRATION (REU)
PUSHBUTTON LRU FAIL
HEADPHONE JACK
KEY INTERLOCK
PTT LINE
MIC CONTROL INPUT FAIL
JACK KEY INTERLOCK
SQL/LAMP TEST
AUDIO/
SIDETONE HFS−700 PHONE MIC TUNE POWER
MIC AUDIO
RECHANNEL LINE
ELECTRONIC SHELF (E2−1) 115V AC
HF−1 AC 28V DC

PRESSURIZING
115V AC
M226 HF−1 TRANSCEIVER (E6−2) CONNECTOR
ESS ELEC
BUS−1 FREQUENCY
SQUELCH TO FLIGHT
SELECT RECORDER
ANALOG) (DIGITAL) CAL-SEL
CALSEL
M227 HF−1 ANTENNA COUPLER
FOR TRAINING PURPOSES ONLY!

P18 LOAD CONTROL

(VERTICAL FIN)
CENTER
HF CALSEL
SQ SSB 4
3 5
2 6
FROM CONTROL
1 7
STAND PANEL AM 0 8
LIGHT 5V AC 9
CONTROL
(P8)

P9−18 HF−1 CONTROL PANEL

Figure 33 HF System-Function
FRA US/T NM Sep 13, 2006 07/HF Sys/L2 Page 57
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

HF SYSTEM - COMPONENT LOCATION

HF−1 CONTROL PANEL,

AFT ELECTRONICS PANEL

HF CALSEL HF−1 POWER,

SQ SSB 4 LOAD CONTROL
FOR TRAINING PURPOSES ONLY!

3 5
2 6 CENTER P18
1 7
AM 0 8
9

HF CONTROL PANEL

Figure 34 HF System-Component Location (Cockpit)

FRA US/T NM Sep 13, 2006 07/HF Sys/L2 Page 58
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

AFT EQPMT AFT ELECTRONIC

DOOR EQPMT RACK, E6

HF ANTENNA COUPLER

FWD
HF ANTENNA COLLINS
HF ANTENNA
COUPLER
LRU FAIL
KEY INTERLOCK
CONTROL INPUT FAIL
FOR TRAINING PURPOSES ONLY!

SQL/LAMP TEST
HFS−700

PHONE MIC

HF TRANSCEIVER

Figure 35 HF System-Component Location (other Areas)

FRA US/T NM Sep 13, 2006 07/HF Sys/L2 Page 59
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

CALSEL-SYSTEMDESCRIPTION
The CALSEL system allows the flight crew to alert an appropriately equipped
ground station via the HF system using the CALSEL encoder control.
the registration number of the calling airplane will be displayed to the operator
on ground. The call signal can be selected on the CALSEL control panel
Activation of the CALSEL encoder control will automatically key the HF radio
system and transmit the airplane CALSEL code on the HF frequency
determined by the HF radio frequency selector.
The transmitted signal contains the registration number of the calling airplane.
It is coded by wire links on the panel connector.
The coded signal consists of a 32 bit word.
The bit states are represented by two audio frequencies: 1285 and 1715 Hz.

CALSEL/CODE Selector
0 - SELCAL received, unable to read, changing to next lower frequency
1 - SELCAL received, unable to read, changing to next higher frequency
2 - WILCO (selected if transmission unreadable at FRA ground station)
3 - Message received but unable to comply with
4 - Airplane on ground, assistance required (e. g. maintenance, flight plan)
5 - Routine calls (e. g. arrivals, departure)
6 - Request crew planning
7 - Request flight plan, MET- report or maintenance assistance
8 - Diversion
9 - Any urgent message
FOR TRAINING PURPOSES ONLY!

NOTE: Code numbers 5 to 9 are related to airplanes in flight.

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COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

HF CALSEL
3 4 5
SQ SSB
2 6
1 7
AM 0 9 8

MIC HI
CALSEL ENCODER FLT
CONTROL PANEL MIC LO
INTPH
SYS
PTT (TO HF
TXFR)
28V DC
CALSEL
SWITCH
K1

AFT ELECTRONIC START

PANEL (P8)

A/C
1
FOR TRAINING PURPOSES ONLY!

CODE
28V DC
BUS NO. 1
CALSEL
P18−2

P18 LOAD CONTROL LOGIC HI

PANEL LOGIC LO
ENCODING
MODULE
1 CDF D−ABWA SHOWN
P8−56 HF/CALSEL CONTROL PANEL
Figure 36 CALSEL-Presentation
FRA US/T NM Sep 13, 2006 07/HF Sys/L2 Page 61
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COMMUNICATIONS B737−300/400/500
HF-SYSTEM
23−11

HF SYSTEM-COMPONENT DESCRIPTION
RADIO COMMUNICATION PANEL (OPTIONAL) Set the frequency in the standby frequency indicator.
 Turn the frequency selectors to set the frequency.
General
− The first digit is always 1.
The radio communication panel (RCP) provides these functions:
The outer knob sets the second two digits (10 MHz and 1MHz) in 1 MHz
 VHF and HF radio selection
increments.
 Active/standby frequency selection The inner knob sets the fourth, fifth, and sixth digits (100 kHz, 10 kHz, and 1
 HF sensitivity control kHz) in 8.33 kHz increments.
 Mode selection to the HF transceiver  Push the frequency transfer switch to change the active and standby
 Off switch. frequencies.
 Controls and Indicators The HF SENS control sets the RF sensitivity level of the HF transceiver.
 Rotate the control to adjust the sensitivity of the HF transceiver.
Operation
The inactive frequency indicator shows a value between 0 and 99.
At power up, Maximum sensitivity is 99. Minimum sensitivity is 0. After a delay, the inactive
 RCP 1 controls VHF 1, frequency indicator shows the inactive frequency again.
 RCP 2 controls VHF 2, and The VHF communication test switch starts a confidence check of the VHF
 RCP 3 controls VHF 3. transceiver (it bypasses the squelch circuit: you hear the background-noise of
Any radio communication panel can control any transceiver. the received signal) .
 Push the radio tuning switch to select the transceiver for that radio  Push the VHF communication test switch to stop the squelch in the VHF
communication panel. transceiver.
− The light above the switch comes on. − You hear static when you push the switch.
Each radio communication panel can tune only one transceiver at a time.  Push the OFF switch to stop the operation of the radio communication
panel.
When you select an off−side radio, two off−side tuning lights come on.
− The switch shows white when it is off.
One light is on the radio communication panel that you use to make the
FOR TRAINING PURPOSES ONLY!

selection. This is the off−side radio. BITE

The other light is on radio communication panel of the radio you select. The radio communication panel continuously does a self−test.
This is the on−side radio. The frequency indicators show PANEL FAIL when there is an internal failure of
the radio communication panel.
The radio communication panel continuously monitors the condition of the
transceiver.
ATTENTION: If the transceiver had failed, the two frequency indicators show
FAIL.

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COMMUNICATIONS B737−300/400/500
HF-SYSTEM
23−11

FREQUENCY OFF−SIDE
TRANSFER TUNING
SWITCH LIGHT
ACTIVE STANDBY
FREQUENCY FREQUENCY
INDICATOR INDICATOR
ACTIVE STANDBY
VHF COMM
TEST
V SWITCH
H C
OFF SWITCH F O
/ PANEL M FREQUENCY
H M SELECTORS
OFF TEST
HF SENSITIVITY F
VHF 1 VHF 3 VHF 2
CONTROL VHF

SEN
HF 1 AM HF 2

1
FOR TRAINING PURPOSES ONLY!

HF RADIO AM SWITCH VHF RADIO

TUNING TUNING
1 INOP SWITCH SWITCHES
INOP PLACARDS ARE OVER THE LEGEND
OF ANY RADIO SELECT SWITCH
THAT IS NOT CONNECTED.

Figure 37 HF Freq.-Radio Control Panel (RCP)

FRA US/T NM Sep 13, 2006 08/HF Sys COMP/L2 Page 63
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COMMUNICATIONS B737−300/400/500
HF-SYSTEM
23−11
HF - TRANSCEIVER HF - ANTENNA
Purpose Purpose
The HF communication transceiver transmits and receives RF signals for voice The HF antenna radiates and receives the RF signal.
communication.
Physical Description
Physical Description The HF antenna is a notch type antenna. It is a U−shaped fiberglass material.
The front panel has these components: The antenna is sealed within the leading edge of the vertical stabilizer.
 Three fault LEDs The antenna receives the feed line from the antenna coupler.
 A squelch/lamp (SQL/LAMP) test push−button
HF - ANTENNA COUPLER
 A microphone jack
 A headphone jack. Purpose
All electrical connections are through connectors at the rear of the transceiver. The HF antenna coupler matches the transceiver 50 ohm impedance output to
the antenna impedance at the set frequency.
Power This decreases the voltage standing wave ratio (VSWR) to less than 1.3:1.
The transceiver must have 115 volts, 400 Hz, 3 phase AC power to operate.
Physical Description
Transceiver RF output is 400 watts peak envelope power (PEP) in the single
The coupler front panel has these components:
sideband (SSB) mode.
 Fill valve
It is 125 watts average in the amplitude modulated (AM) mode.
 Electrical connector to transceiver
In the AM mode the transceiver transmits the amplitude modulation equivalent
(AME) . AME is the carrier frequency plus the upper side band.  Coaxial connector to transceiver
 Pressure nozzle
Indications
The rear panel has the antenna feedline connector.
 The LRU FAIL LED comes on red for a failure in the HF transceiver.
 The KEY INTERLOCK LED comes on red when the transceiver keys and Operation
there is a failure in the HF coupler. Transmission is not possible at this time. The coupler uses 115V AC to operate.
 The CONTROL INPUT FAIL LED comes on red if there is no input from the It does not need special cooling.
FOR TRAINING PURPOSES ONLY!

control panel or if the control panel input goes invalid. The coupler tunes in the aeronautical frequency range of 2 to 29.999 MHz.
Tuning occurs in 2 to 4 seconds, 15 seconds maximum
BITE
CAUTION: YOU MUST PREPARE EACH HF ANTENNA COUPLER FOR
Push the SQL/LAMP TEST push button to stop the operation of the squelch
REMOVAL.
circuit and to hear background noise through the headphones.
IF YOU DO NOT PREPARE FOR THE REMOVAL, YOU CAN
This test also grounds the RF sensitivity and makes the front panel LEDs come CAUSE DAMAGE TO THE INTERNAL PARTS OF THE HF
on. ANTENNA COUPLER.
It is important that the antenna tuning elements inside the coupler have to be in
the home position before you move the coupler.

FRA US/T NM Sep 13, 2006 08/HF Sys COMP/L2 Page 64

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF-SYSTEM
23−11

COLLINS ANTENNA
FEEDLINE
LRU FAIL CONNECTOR
HF - ANTENNA
KEY INTERLOCK

CONTROL INPUT FAIL

SQL/LAMP TEST REAR VIEW

PHONE MIC

HF - TRANSCEIVER FILL VALVE

FOR TRAINING PURPOSES ONLY!

PRESSURE NOZZLE
COAXIAL CABLE
CONNECTOR
TO TRANSCEIVER
ELECTRICAL
CONNECTOR TO
TRANSCEIVER HF - ANTENNA COUPLER

Figure 38 HF System-Components
FRA US/T NM Sep 13, 2006 08/HF Sys COMP/L2 Page 65
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

HF TUNING SYSTEM FUNCTION

General Tune
These are the HF communication system functional modes: The tune occurs in these steps:
 Home  Tune A (resonance)
 Receive/standby  Tune B (Load)
 Tune  Tune C (VSWR)
 Receive/operate To start tune mode A, key the transceiver.
 Transmit The transceiver microprocessor sets the AM mode.
The HF system controls the modes in sequence. The key is latched. Reduced RF power goes to the antenna coupler.
The modes do not change until all necessary conditions for them do occur. A 1kHz tone sounds as tuning occurs.
The radio tunes in 6 to 8 seconds.
HF MODES DESCRIPTION
The antenna coupler discriminator circuit operates to set phase differences
Home Mode between the RF voltage and current.
The home mode starts at power−up or when a new frequency is set. Tuning elements are set for zero phase difference.
The antenna tuning elements move to the HOME position. During tune mode B, tuning elements are set to a total impedance of 50 ohms
The elements are in a position for minimum attenuation of incoming signals. or less and resonant.
During tune C, tuning elements move so that RF power loading generates a
CAUTION: YOU MUST PREPARE EACH HF ANTENNA COUPLER FOR
VSWR less than 1.3:1.
REMOVAL.
IF YOU DO NOT PREPARE FOR THE REMOVAL, YOU CAN The reflected power is less than 2 watts RF.
CAUSE DAMAGE TO THE INTERNAL PARTS OF THE HF
Receive/Operate
ANTENNA COUPLER.
The receive/operate mode occurs when tune C is complete.
It is important that the antenna tuning elements inside the coupler are in the
home position before you move the coupler. Key latch is removed. Tuning RF power is off.
The 1 kHz tone stops. The system is ready for reception or transmission.
FOR TRAINING PURPOSES ONLY!

Receive/Standby Mode
The receive/standby mode starts when the tuning elements are in the HOME Transmit
position. The pilot keys the microphone to transmit.
In the receive/standby mode, the HF system can receive RF at the set The coupler adjusts tuning elements to keep VSWR less than 1.3:1 during
frequency. modulated transmission.
The system is ready to key for tuning at any time. The audio tone does not sound at this time.

FRA US/T NM Sep 13, 2006 09/HF Sys TUNING/L2 Page 66

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

NO

HOME PRESS
HOME WITHIN YES RECEIVE/ TO YES
POWER ON SEQUENCE 15 STANDBY TALK
SECONDS ?
?

NO
COUPLER
RETUNE FAULT

AUDIO
RESET:
TONE TUNE
HOME-STANDBY DURING
TUNE

YES

FREQUENCY NO
CHANGED
?

TUNED
RECEIVE/ NO COUPLER YES WITHIN
FOR TRAINING PURPOSES ONLY!

OPERATE ARCING 15
? SECONDS
?
YES NO
YES
PUSH
TRANSMIT TO
TALK
? RESET: COUPLER
FAULT
HOME-STANDBY
NO

Figure 39 HF-Functional Modes

FRA US/T NM Sep 13, 2006 09/HF Sys TUNING/L2 Page 67
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

HF SYSTEM FUNCTION
General Listen for audio from the HF radio on the speaker or headset.
You use these components to operate the HF radio:  Adjust the volume control switches on the ACP for a comfortable sound
 Hand microphone or headset level.
 Radio communication panel  Use the sensitivity control on the RCP to adjust the sensitivity of the HF
transceiver.
 Control wheel mic switch
 Audio control panel Transmit Operation
Make sure the active frequency display shows the frequency you want to
OPERATING PROCEDURE
transmit and that this frequency is a valid transmit frequency.
You use the RCP and the ACP to receive transmissions on the HF radio.
 Push the microphone selector switch on the ACP for the HF radio.
 On the audio control panel, push the receiver volume control for the HF
 Listen for transmissions on the frequency you selected.
radio.
 When the frequency is clear, push and release the PTT for the microphone.
 Turn the control to adjust the volume from the HF radio.
This causes the HF coupler to tune to the transmission frequency.
You hear audio on the headset and the flight interphone speakers.
While the coupler tunes, the HF transceiver supplies a 1 kHz tone.
 To hear sound from the flight interphone speakers, push the SPKR
(SPeaKeR) volume control to turn on the speaker.  You hear this tone on the speaker and in the headset.
 Turn the control to adjust the volume of sound from the speaker. Normally, it takes several seconds for the coupler to tune.
 Use the on/off control to turn on the RCP.  When the 1 kHz tone stops, the HF system is ready to transmit.
When you first turn it on, the radio communication panel tunes the VHF radio.  When the frequency is clear and you want to transmit a message, key the
mic and speak into it.
 Push the HF 1 switch to make the radio communication panel tune the HF
radio.  You hear sidetone in the headphone and muted sidetone from the flight
interphone speaker.
A light above the switch comes on to show which radio the panel controls.
The flight interphone system mutes the sidetone to the speaker when you use
The frequency displays show HF radio frequencies (2.000 to 29.999 MHz).
the boom mic or the hand mic.
The HF radio uses the frequency in the active frequency display.
FOR TRAINING PURPOSES ONLY!

You can continue to transmit and receive on the frequency you selected.
 Use the frequency selectors to tune the radio to a new frequency.
 When you select another frequency and key the mic to transmit, the HF
The standby frequency display shows the new frequency. coupler tunes again.
 When you are sure the frequency is correct, push the frequency transfer  You hear the 1 kHz tone while it tunes.
switch.
The active frequency display shows the new frequency then the HF radio uses Non−Normal Indications
the new frequency.  If you hear the 1 kHz tone for more than 15 seconds when the coupler
tunes, there may be a coupler fault.
NOTE: When you select a new frequency, the HF coupler drives its tuning
elements to the home position.  If the tone only lasts as long as you key the microphone, you may have
tuned a frequency which is outside the frequency range for the HF
transceiver.

FRA US/T NM Sep 13, 2006 11/HF Sys OPER/L2 Page 68

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

WARNING: MAKE SURE THAT PERSONNEL STAY A

MINIMUM OF 10 FT (3 M) AWAY FROM THE MIC SWITCH
VERTICAL STABILIZER WHEN THE HF
SYSTEM TRANSMITS.
RF ENERGY FROM THE HF ANTENNA CAN
CAUSE INJURIES TO PERSONNEL.

WARNING: DO NOT OPERATE THE HF SYSTEM WHILE

THE AIRPLANE IS REFUELED OR R/T
DEFUELED.
AN EXPLOSION CAN CAUSE INJURIES TO
PERSONNEL AND DAMAGE TO THE
AIRPLANE.

AUDIO CONTROL PANEL HAND

MICROPHONE CONTROL WHEEL

PTT SOURCE

MIC SELECTOR
ACTIVE STANDBY
FOR TRAINING PURPOSES ONLY!

V
H C
F O 1−HF
/ PANEL M
H OFF M
TEST
F VHF 1 VHF 3 VHF 2 VHF
SEN
HF 1 AM HF 2 AUDIO CONTROL PANEL
(HF SELECT)
RADIO COMMUNICATION PANEL
Figure 40 HF System-Function
FRA US/T NM Sep 13, 2006 11/HF Sys OPER/L2 Page 69
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

HF SYSTEM - BITE
Radio Communication Panel BITE Indication
When you push the HF switch on the radio communication panel (RCP), the These are examples of failures of the HF transceiver:
display usually shows an HF radio frequency.  The voltage from the power supply is low
The range of HF radio frequencies is 2.000 MHz to 29.999 MHz.  The microprocessor has a failure
If the built−in test equipment in the RCP senses a failure, you see one of these  The frequency synthesizer is not locked−on
displays:
 The output power of the RF transmitter is low
 FAIL FAIL
The KEY INTERLOCK light comes on when you key the transceiver and the
 PANEL FAIL key interlock signal from the coupler is open.
If the RCP receives no signal from the HF transceiver, both displays show The HF antenna coupler opens the key interlock signal if one of these
frequency. conditions occurs:
This occurs when one of these conditions is true:  The power supply in the HF antenna coupler is not good
 There is no HF transceiver  The tuning reactance is not in tolerance
 The HF transceiver has no power  The time to tune the HF antenna coupler is too long
 The HF transceiver can not send ARINC 429 data to the RCP The CONTROL INPUT FAIL light comes on when the HF transceiver does not
 The RCP does not receive the ARINC 429 data from the HF transceiver receive a signal from the radio communication panel.
 Wiring from the HF transceiver to the RCP is bad This occurs when one of these conditions is true:
If the RCP receives the FAIL WARN signal from the HF transceiver, the display  The RCP is off
shows FAIL in both displays.  The RCP has no power
This occurs when the BITE in the HF transceiver senses that the transceiver  The RCP can not send the ARINC 429 data to the HF transceiver
has a failure.
 The HF transceiver does not receive the ARINC 429 data from the RCP
ATTENTION: If the RCP has a failure, the display shows PANEL in the active  The wiring from the RCP to the HF transceiver is bad
display and FAIL in the standby display.
HF Transceiver Built−In Test
HF Transceiver BITE Indication
FOR TRAINING PURPOSES ONLY!

The HF transceiver has a built−in test.

Lights on the front of the HF transceiver show these failures:
To start the test, push the SQL/LAMP TEST switch on the front of the
 LRU FAIL transceiver.
 KEY INTERLOCK During the test, the transceiver does these operations:
 CONTROL INPUT FAIL  Turns on the lights on the front panel.
The LRU FAIL light comes on if the HF transceiver has a failure.  Stops the audio squelch circuit in the receiver.
 Sets the RF sensitivity to a set quantity.
The test stops when you release the switch.

FRA US/T NM Sep 13, 2006 12/HF Sys BITE/L2 Page 70

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
HF- SYSTEM
23−11

ACTIVE STANDBY DISPLAY

CONDITION
V ACTIVE STANDBY
H
F C VALID FREQUENCY FOR THE HF RADIO
/ O 7.160 2.800
PANEL M (2.000 TO 29.999)
H TEST
M
OFF
F VHF 1 VHF 3 VHF 2 7.160 2.800 RCP RECEIVES NO SIGNAL
VHF
SEN
FROM THE HF TRANSCEIVER
HF 1 AM HF 2
FAIL FAIL HF TRANSCEIVER FAILURE
RADIO COMMUNICATION PANEL
PANEL FAIL RCP FAILURE

COLLINS

LRU FAIL

KEY INTERLOCK
LIGHT ON CONDITION
CONTROL INPUT FAIL

LRU FAIL HF TRANSCEIVER FAILURE

SQL/LAMP TEST
FOR TRAINING PURPOSES ONLY!

HF ANTENNA COUPLER, WIRING, OR ANTENNA

KEY
PHONE MIC FAILURE. NOTE: YOU MUST KEY THE
INTERLOCK
HF TRANSCEIVER TO DETECT THE FAILURE

CONTROL HF TRANSCEIVER RECEIVES NO SIGNAL

INPUT FAIL FROM THE RCP

HF TRANSCEIVER
Figure 41 HF System-BITE
FRA US/T NM Sep 13, 2006 12/HF Sys BITE/L2 Page 71
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
SELCAL
23−28

23−28 SELCAL SYSTEM

SELCAL SYSTEM PRESENTATION
The SELCAL (SELective CALling) system allows a ground station, with tone SELCAL Control Panel
transmitting equipment, to call a specific airplane. The SELCAL control panel receives the signals that come from the SELCAL
When the correct tone combination is received, the airplane SELCAL decoder decoder unit.
unit signals the flight crew by a SELCAL light and an electronic chime. The alert light comes on for the transceiver that receives the call. Push the
The SELCAL system eliminates the necessity of continuous monitoring of the alert light switch to reset the decoder channel.
communication system by the flight crew.
Audio
Visual indication is provided by CALL indicators on the audio selector panels or
by a SELCAL light on the VHF COMM/NAV control panel. The SELCAL decoder receives audio from the HF and VHF transceivers.
The electronic chime is part of the aural warning system.
HF and VHF Transceivers
When the ground station operator wants to call a specific airplane using the The HF and VHF transceivers receive the SELCAL signal and send it to the
SELCAL system, the four−tone code which has been assigned to the SELCAL decoder.
airplane is added to the audio transmitted from the ground station.
This code is received by a communication system and sent to the SELCAL SELCAL Coding: Shorting Receptacle
decoder unit. If the four−tone code received is identical to the code entered on A SELCAL shorting receptacle gives the airplane its SELCAL code by jumper
the SELCAL decoder, the flight crew will be alerted by the SELCAL light and wires.
electronic chime. The SELCAL coding switch is behind the SELCAL decoder on the E-2 rack.
On airplanes with call indications on the audio selector panels, the call is reset
by pushing the call indication for the system with the call on any audio selector Remote Electronics Unit (REU)
panel. For airplanes without call indications on the audio selector panels, the The REU sends a signal to the aural warning unit.
SELCAL reset button is on the VHF COMM/NAV control panel. The aural warning unit makes a high/low chime signal.

Power Discretes
The 28v DC bus 1 supplies power to the SELCAL decoder. The SELCAL decoder unit sends call discretes to the SELCAL control panel or
FOR TRAINING PURPOSES ONLY!

to the audio control panels. There is a different discrete for each transceiver.
SELCAL Decoder Unit The SELCAL control panel or audio control panels send call reset discretes to
The SELCAL decoder unit monitors for audio tones. If the tones are the same the SELCAL decoder unit.
as the code, the decoder sends a signal to the control panel. The SELCAL decoder unit supplies a discrete signal to make a high/low chime
The decoder also sends a ground to the SELCAL aural warning relay. in the flight compartment.
This relay gives power to the REU to send a signal to the aural warning unit. The signal will be routed to the SELCAL aural warning relay.
The SELCAL decoder is on the E-4 rack in the electronic equipment The relay sends a 28v DC signal through the remote electronics unit to the
compartment. aural warning module which gives a single, high/low chime in the flight
compartment.

FRA US/T NM Sep 12, 2006 13/SELCAL Sys/L2 Page 72

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
SELCAL
23−28

28V DC HF 1
BUS 1
SELCAL HF 2
C C
A CALL SET VHF 1
P18 CIRCUIT 1−VHF−2−VH
BREAKER PANEL VHF 2
VHF 3
AUDIO CONTROL PANEL (OR
SELCAL CONTROL PANEL)
AUDIO
HF 1
HF 2
HF 1 TRANSCEIVER VHF 1 CALL
RESET
VHF 2
VHF 3
AUDIO
REU

HF 2 TRANSCEIVER CHIME HI/LO

CONTROL A CHIME
AUDIO
SELCAL AURAL REU AURAL
2 INHIBIT RELAY WARNING
3
VHF 1 TRANSCEIVER 4 MODULE
5
6
7
FOR TRAINING PURPOSES ONLY!

AUDIO 8 IN AIR AND RA <1000ft

9
SELCAL 10 LH inb WHEEL SPEED >60kts
CODE: 11
12 CHIME CONTROL
VHF 2 TRANSCEIVER 13
14
15
16
AUDIO 17
1

M1454 SHORTING
VHF 3 TRANSCEIVER SELCAL DECODER UNIT RECEPTACLE (E2−1)

Figure 42 SELCAL-System Presentation

FRA US/T NM Sep 12, 2006 13/SELCAL Sys/L2 Page 73
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
SELCAL
23−28

28V DC
ELEX BUS 1 INTERRUPTED CIRCUITS SIGNAL
SELCAL 1
STEADY SIGNAL
P18−2 CB PANEL SELCAL 1 CLOSED CIRCUIT SIGNAL 1
118 00 TFR 118 00 A 28V DC IN 1 AAU CARD HI−LO
COMM COMM
CHIME
SEL
CAL M1353 REMOTE
RESET 1
ELECTRONIC UNIT M315 AURAL
AUDIO OSCILLATOR (E2−1) WARNING UNIT
P8−2 VHF COMM INPUT 1 SELECTOR RELAY
CONTROL PANEL
HIGH SWITCHES
SELCAL & REEDS
AUDIO
LOW AUDIO
GROUND 1
M149 VHF COMMUNICATION 1
TRANSCEIVER (E2−1)

DECODER 1

28V DC
ELEX BUS 2 INTERRUPTED CIRCUITS SIGNAL
SELCAL 2 INTERRUPTED SIGNAL
STEADY SIGNAL
P6−1 CIRCUIT BRKR PANEL SELCAL 2
CLOSED CIRCUIT SIGNAL
118 00 TFR 118 00 A
28V DC IN 2
FOR TRAINING PURPOSES ONLY!

COMM COMM INTERNALS

SEL SAME AS
CAL
RESET 2 DECODER 1 ABOVE

P8−2 VHF COMM

HIGH CONTROL PANEL AUDIO INPUT 2
SELCAL
AUDIO
LOW AUDIO GRD 2
DECODER 2
M150 VHF COMMUNICATION 2
TRANSCEIVER (E2−1)
M25 SELCAL DECODER (E2−2)

Figure 43 SELCAL-System Function (Config. 1)

FRA US/T NM Sep 12, 2006 13/SELCAL Sys/L2 Page 74
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
SELCAL
23−28

ELEX 28V DC
+5V
BUS 1 SELCAL
POWER
P18−2 CIRCUIT SUPPLY
BREAKER PANEL
1 AIRPLANES WITH
VHF−3
K7 K6 K5 K4 K3 K2 K1
2 AIRPLANES WITH
REM HF−1
M315 AURAL ELECTR 3 D2559 PIN 2−17
WARNING UNIT WIRE INSTALLED
LOGIC 0
WIRE DELETED
SELCAL 1 NC−C1 LOGIC 1
A
NC−C1

P8−2 VHF COMM/NAV 1

CONTROL PANEL FREQ
SELCAL 2 GENERATOR
A CIRCUIT BUFFER

3
RESET A10 2
CIRCUIT SELCAL DECODER−TEAM B10 3
NC−C1
P8−3 VHF COMM/NAV 2 C10 4
CONTROL PANEL NC−A2
D10 5
SELCAL FILTER A11 6
HI B11 7
LOW C11 8
AUDIO CHANNEL 1 CODE
M149 VHF SELCAL D11 9
INPUT
COMMUNICATION 1 HI CHANNEL 2 SELECTION A13 10
FOR TRAINING PURPOSES ONLY!

TRANSCEIVER SAME AS CHANNEL 1

AUDIO LOW A-D B13 11
CONV C13 12
M150 VHF CHANNEL 3
COMMUNICATION 2 SAME AS CHANNEL 1 D13 13
SELCAL TRANSCEIVER A15 14
HI B15 15
1
LOW C15 16
AUDIO CHANNEL 4
SAME AS CHANNEL 1 D15 17
M411 VHF−3 8 BIT
TRANSCEIVER SELCAL HI PROC B9 1
2 CHANNEL 5 UNIT
NC M1454
LOW SAME AS CHANNEL 1
AUDIO SHORTING
M226 HF−1 RECEPTACLE
TRANSCEIVER M1451 SELCAL DECODER (E2−1) (E2−1)

Figure 44 SELCAL-System Function (Config. 2)

FRA US/T NM Sep 12, 2006 13/SELCAL Sys/L2 Page 75
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
SELCAL
23−28

SELCAL DECODER
MOTOROLA Selcal Decoder
CODE
Two separate decoders, in a common case, make up the dual SELCAL
DISPLAY
decoder unit.
WINDOW
One decoder receives the audio input from the VHF−1 transceiver, the other
decoder from the VHF−2 and VHF−3 transceivers.
Each decoder consists of an audio amplifier, a resonant reed circuit, a DC A
amplifier and control relays. CODE
SELECT
TEAM Selcal Decoder (A−H, J−M)
The SELCAL decoder is a five channel multiplexed unit.
Four of the decoder channels are connected to the VHF−1, VHF−2, VHF−3, CODE SELECTOR KNOB
and HF−1 transceivers, respectively. The other channel is not used.
(EXAMPLE)
The decoder consists of compressor amplifiers, filters, an analog to digital
converter, a microprocessor and control relays.
Every channel will recognize the unique four tone code assigned to the
airplane.
The assigned code is pin programmable and determined by airplane wiring to
SELCAL decoder connector D2555B or connector D849. NO. 2 DECODER
NO. 1 DECODER SELECTOR KNOBS
The four tone code is resolved with a 16−bit binary word.
SELECTOR KNOBS
Four bits of the word determine each tone.
A coding receptacle is wired to implement the unique 16 bits of this code for
the airplane.
This receptacle is mounted external to the SELCAL decoder and connected to
it with a short cable.
FOR TRAINING PURPOSES ONLY!

Thus the SELCAL decoder can be replaced without affecting the code.
The coding receptacle is placed on the rack behind the decoder.
A green and a red and five yellow LED’s are located at the front panel of this
decoder.
Push the test knob on the front panel and check the indication:
 all LED’s come on for about 3s (lamp test) DUAL SELCAL DECODER − MOTOROLA
 subsequentially all LED’s come on step by step (test sequence)
 at the end of the test the green GO LED comes on for about 3 s (no failure)
 in case of existing failure the red NO GO LED comes on.

FRA US/T NM Sep 12, 2006 13/SELCAL Sys/L2 Page 76

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
SELCAL
23−28

LOAD CONTROL FORWARD

SELCAL−2 POWER (SELCAL DECODER)
ELECTRONICS
CENTER, P6 ELECTRONIC SECTION
EQUIPMENT
AUDIO CONTROL
RACK, E2 STAND
CONTROL
PANEL, P8
SELCAL
AURAL
CHIME
WARNING
MODULE

SELCAL−1 POWER
LOAD CONTROL
CENTER, P18
FWD AUDIO CONTROL PANEL (OPTIONAL)
AURAL WARNING MODULE

118.000 TFR 136.000

COMM COMM
SEL
CAL
PUSH TO
RESET
FOR TRAINING PURPOSES ONLY!

FREQUENCY SELECT PANEL (OPTIONAL)

SELCAL

VHF 1 VHF 2 VHF 3 HF 1 HF 2

PRESS TO RESET
DUAL SELCAL DECODER − SELCAL DECODER − TEAM
MOTOROLA NA−135 SELCAL CONTROL PANEL (OPTIONAL)
Figure 45 SELCAL System-Component Location
FRA US/T NM Sep 12, 2006 13/SELCAL Sys/L2 Page 77
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

23−27 ACARS
ACARS-INTRODUCTION Abbreviations and Acronyms
ACARS − Aircraft Communications Addressing and Reporting System
Purpose ACMS − Aircraft Condition Monitoring System
The ACARS is a datalink system. It lets you transmit messages and data ADL − Airborne Data Loader
between an airplane and an airline ground base.
ARINC − Aeronautical Radio InCorporated
 A message from the airplane to the airline ground base is called a downlink.
ATC − Air Traffic Control
 A message from the airline ground base to the airplane is called an uplink.
ATE − Automatic Test Equipment
To reduce crew workload, ACARS sends reports when necessary and at
scheduled times of the flight. BC − BroadCast
These are typical ACARS reports: BITE − Built−In Test Equipment
 Crew related operational data DEU − Display Electronics Unit
 airplane movement reports [Out, Off, On, In (000I) times] DB − DataBase
 Engine performance data for trend-monitoring DIP − Dual Inline Package
 Flight status ETA − Estimated Time of Arrival
 Maintenance items FDAU − Flight Data Acquisition Unit
FMCS − Flight Management Computer System
ID − IDentification
LCD − Iiquid Crystal Display
LED − Light Emitting Diode
MISC − MISCellaneous
MSG − MeSsaGe
MU − Management Unit
FOR TRAINING PURPOSES ONLY!

NOTAM − NOtice To AirMen

NVM − Non−Volatile Memory
000I − OUT, OFF, ON, IN
PARAMS − PARAMeterS
PCMCIA − Personal Computer Memory Card International Association
PREFLT − PREfFLghT
RAM − Random Access Memory
RCP − Radio Communications Panel
RCV − ReCeiVer

FRA US/T NM Sep 21, 2006 15/ACARS INTRO/L1 Page 78

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

DREAM-AIRLINE

ACARS DATA/ ACARS DATA AIRLINE

VOICE STATION LINK CONTROL OPERATIONS
FOR TRAINING PURPOSES ONLY!

Figure 46 ACARS-Introduction
FRA US/T NM Sep 21, 2006 15/ACARS INTRO/L1 Page 79
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS-GENERALDESCRIPTION
General
The ACARS is a voice and data communication system to manage flight plan
data and maintenance data between the airplane and the airline.
These are the components of the ACARS:
 CDU
 ACARS program switch modules
 MU
You use the CDU to control the operation of the ACARS and to display ACARS
messages.
The ACARS program switch modules contain DIP switches. These switches
identify the airplane.
The ACARS MU receives the ground−to−air digital messages (uplink) and
controls the transmission of the air−to−ground digital messages (downlink) .
ACARS connects to these components of other systems:
 VHF transceiver to transmit to and receive data from the ground
 Printer to print ACARS reports and messages
 Proximity switch electronics unit which sends discrete signals for out, off, on
and in (000I)
 Remote electronics unit to distribute the chime and light annunciation for an
incoming ACARS message.
ACARS also connects to these systems to upload information from the airline
operations or download information to the airline operations:
 Flight management computers
FOR TRAINING PURPOSES ONLY!

 Flight data acquisition unit

 Data loader control panel
The ACARS MU is on the E3−3 shelf.
The ACARS program switch modules are on the E3−3 shelf behind the ACARS
MU.

FRA US/T NM Sep 21, 2006 15/ACARS INTRO/L1 Page 80

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

UPLINK/DOWNLINK
MK II DATA

MU PASS
VHF-3
TRANSCEIVER
CMU HW FAIL

LOAD SW

XFER
BUSY
XFER
COMP
XFER
CONTROL DISPLAY FAIL
CHIME
UNITS APM FAIL

REMOTE AURAL
ELECTRONICS WARNING
UNIT MODULE

PRINTER
FOR TRAINING PURPOSES ONLY!

AIRPLANE PROGRAMMABEL
MODULE (APM)
SHORTING RECEPTACLE UPLOAD/ FLIGHT MANAGEMENT
DOWNLOAD COMPUTER SYSTEM
PROGRAM PINS DATA FLIGHT DATA
ACQUISITION UNIT
OOOI-SENSOR DATA DATA LOADER
CONTROL PANEL
ACARS MANAGEMENT UNIT
Figure 47 ACARS - General Description
FRA US/T NM Sep 21, 2006 15/ACARS INTRO/L1 Page 81
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COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS SYSTEM - INTRODUCTION

The ACARS (Aircraft Communications Addressing and Reporting System) is a Airplane Programmable Module (APM)
digital data−link system that operates between an airplane and a ground−based The APM contains an electrically erasable programmable read-only memory
network of receiver−transmitter stations and central processing stations. (EEPROM).
The transmission medium is generally a single frequency in the VHF frequency The APM provides aircraft registration, aircraft type, ICAO-address and
range. The VHF−3 is used by the ACARS to transmit and receive messages. equipment configuration information.
By automatically transmitting routine messages, the ACARS reduces crew Programming of the APM is achieved by ACARS-CMU.
workload.
To remember: The digital flight data acquisition until (DFDAU) provides the
Also, lengthy voice transmissions to communicate with the ground are reduced ac-registration for ACARS. The APM ac-registration is used to verify those
with the ACARS. data.
The airborne ACARS system is used to transmit and receive data or Maintenance personal is provided with the specific password to access APM
messages. programming functions on MCDU-pages.
Messages for transmission can be generated automatically or can be input Note: Programming for APM is not required when CMU was replaced.
manually by crew members.
The ACARS will then properly tune and key the VHF−3 transceiver for the data
transmission.
The VHF−3 can also be used for voice transmission in the ACARS voice mode
of operation.
Voice communications can be simplified by use of the ACARS.
The crew can send a downlink message to request to talk to a party on the
ground.
The message can even contain the telephone number of the party.
The ground can then make the arrangements, uplink the frequency the crew
needs to tune in, and command the ACARS to switch automatically to voice
mode.
FOR TRAINING PURPOSES ONLY!

The ACARS MU (Management Unit) controls all functions of the airborne

ACARS system.
The MU interfaces with many other systems on the airplane.
Crew interface to the unit is via the FMC Multi−purpose Control Display Units
(MCDU) .
The MU is installed on the E2−3 electronics shelf.
It is fastened to the equipment rack by two hooks at the front and a rack and
panel connector on the rear.

FRA US/T NM Feb 15, 2007 16/ACARS−GEN/L2 Page 82

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COMMUNICATIONS B737−300/400/500
ACARS
23−27

115V AC
BUS 1 ACARS AC POWER
SUPPLY DATA IN
28V DC TX/RX DATA
HOT BAT BUS ACARS DC
DATA OUT
P18−2 LOAD CONTROL CENTER

OUTPUT BUS 1 FREQUENCY SELECT PORT A

TUNING DATA
ACARS DATA
CDU−L INPUT DATA KEYLINE
P9−65 MCDU−L DATA KEYLINE RETURN
VHF−3 CONTROL DISCRETES
VOICE/DATA SELECT
ACARS DATA FREQ PORT SELECT
FMC DATA
M411 VHF−3 XCVR
M1175 FMC

ACARS DATA ACARS MODE INPUT COMMAND

PRINTER STATUS REMOTE VOICE/DATA SWITCH VOICE/DATA OUTPUT COMMAND
P8−54 ACMS PRINTER PROGRAM PIN COMMON DEDICATED ACARS INPUT
AUTO/MANUAL CHANGEOVER P8 VHF−1 (−2,−3) CONTROL PANEL
54
53
52 AIRPLANE TYPE /
SHELF AIRLINE I.D. ALPHA HI−LO
+28V VOICE GO−AHEAD CONTACT
WIRING 2 CHIME
1
GND LOGIC ZERO SOURCE
M315 AURAL WARN MODULE
SHORTING RCPT (E2−3) GROUND GND REMOTE
SENSING A2 A1 ELECTRONICS UNIT
SQUAT
(R279) ON/OFF SENSOR VOICE GO−AHEAD ANNUNCIATOR LIGHT VHF−3 INDICATOR LIGHT
AFT CLOSED
CARGO AIR A3
P8 CAPT (F/O,OBS) AUDIO SELECTOR
DOOR SET PANEL
C1
C2
FWD PARKING
CARGO BRAKE VOICE GO−AHEAD ALERT RESET VHF−3 PTT
DOOR (R274) OFF C3 M1353 REMOTE ELECTRONICS UNIT

RSV
MK II ACARS DATA
FMC− DATA
FWD LANDING GEAR LOGIC SHELF
SERVICE (E11) MU PASS
FMC
DOOR CMU HW FAIL
FOR TRAINING PURPOSES ONLY!

LOAD SW
OUTPUT BUS 2
AFT IN/OUT
XFER
BUSY

SERVICE XFER ACARS DATA

SENSORS COMP
CDU−R INPUT
DOOR XFER
FAIL

APM FAIL

R319 EQUIP DOOR RELAY P9−66 MCDU−R

AFT
ENTRY
DOOR
ACMS DATA ACARS DATA
FWD AIRPLANE REGISTRATION
ENTRY UTC (TIME)
DOOR M675 DFDAU (DFDAMRU)
OPEN OPEN
OPEN
DATA LOADER
DOOR WARN 28V DC A/C REG ACARS DATA
DATA
(52−71−00) ICAO-ADDR
SYS-CONFIG ENABLE DISCRETE DATA LOADER ENABLE
S196 FWD S197 ELEX
M278 MISC SOLID STATE ACCESS DOOR ACCESS DOOR APM (E-2) P23−13 AIRBORNE DATA LOADER
SWITCHING MODULE (E3−2) SW (STA 240) SW (STA 338L) M1109 ACARS MANAGEMENT UNIT (E2−3)
Figure 48 ACARS Architecture
FRA US/T NM Feb 15, 2007 16/ACARS−GEN/L2 Page 83
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COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS - COMPONENT LOCATION

MENU
<FMC
MULTIPURPOSE
<ACARS
<ACMS
CONTROL
DISPLAY UNIT
(MCDU)

INIT
REF RTE CLB CRZ DES BRT MULTIPURPOSE
MENU LEGS DEP HOLD PROG EXEC
CONTROL
ARR DISPLAY UNIT DATA LOADER SELECT PANEL
N1
LIMIT FIX A B C D E (MCDU) (OPTIONAL)
PREV NEXT
D PAGE PAGE F G H I J M
S S
P G
L 1 2 3 K L M N O
F O
A F
I S
L 4 5 6 P Q R S T T
7 8 9 U V W X Y

. 0 +/− Z SP DEL / CLR

FLIGHT COMPARTMENT
MULTIPURPOSE CONTROL
DISPLAY UNIT (MCDU)
FOR TRAINING PURPOSES ONLY!

DATA

VHF 1 VHF 3 VHF 2

DATA LOADER
RADIO COMMUNICATION PANEL (RCP) (MULTI PURPOSE DISK DRIVE UNIT)

Figure 49 ACARS-Component Location Cockpit

FRA US/T NM Sep 22, 2006 19/ACARS Loc/L2 Page 84
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COMMUNICATIONS B737−300/400/500
ACARS
23−27

MK II
MU PASS

ACARS CMU HW FAIL

LOAD SW
MANAGEMENT UNIT, XFER
ELECTRONIC BUSY
XFER
EQUIPMENT RACK E2−3 COMP
XFER
FAIL
APM FAIL
FOR TRAINING PURPOSES ONLY!

ACARS MANAGEMENT UNIT (CONFIG 1) ACARS MANAGEMENT UNIT (CONFIG 2)

Figure 50 ACARS-Component Location Equipment Rack

FRA US/T NM Sep 22, 2006 19/ACARS Loc/L2 Page 85
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COMMUNICATIONS B737−300/400/500
ACARS
23−27

MESSAGE PRESENTATION
The ACARS ERROR/ADVISORY messages (priority 2) are shown, when the
The MCDU Scratch Pad (SP) display shows messages in the following priority:
ACARS system is selected on the MCDU. Most of them can be cleared by
1. user entries pressing the CLR-key on the MCDU (see chart).
2. ERROR/ADVISORY messages
3. Label 270 messages

ACARS Error/Advisory Messages Chart

Message Text Trigger Condition Reset Condition

NO COMM, LSK that initiates a downlink is pressed while MU is in a 5 seconds or ” CLR ” key pressed or data entry
MSG NOT GEN NO COMM condition.
VOICE MODE, LSK that initiates a downlink is pressed while MU is in 5 seconds or ” CLR ” key pressed or data entry
MSG NOT GEN VOICE Mode.
PRINTER FAIL LSK that initiates a print is pressed, and the printer cannot 5 seconds or ” CLR ” key pressed or data entry
accept a message.
INVALID ENTRY Invalid data entry CLR key pressed or valid data entry
NO A/C REG, MU has not received the A / C Registration Number from the A / C Registration Number from DFDAMRU (Cold Start)
MU IN STBY DFDAMRU (ACMS−system)
BUFFER FULL, LSK that initiates a downlink is pressed, and the downlink 5 seconds or ” CLR ” key pressed or data entry
MSG NOT GEN buffer is full.
AUTO/MAN Manually selected VHF data frequency differs from fre- Select correct frequency or ” CLR ” key or data entry
FREQ MISMATCH quency indicated by automatic frequency select logic.
NO LAT/LON, MU is not receiving latitude and longitude data from aircraft VHF data frequency manually selected or aircraft starts
USE MAN FREQ IRS and FMC broadcast data or ” CLR ” key pressed or data entry
FOR TRAINING PURPOSES ONLY!

BAD H/W PART NUM Hardware part number is invalid Hardware part number
AIRCRAFT TYPE Aircraft type pins are not set for 737−330/430/530 aircraft Reconfigure pins and
MISMATCH reset MU
ACRFT REGNUM Aircraft registration number initially received from broadcast Install MU on proper aircraft or modify database
DBASE FAIL does not match database
The Label 270 messages are shown on the MCDU display.

Label 270 Chart

FRA US/T NM Sep 22, 2006 20/ACARS MSGs/L2 Page 86

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COMMUNICATIONS B737−300/400/500
ACARS
23−27

Message Text MCDU Trigger Condition Reset Condition

ACARS CALL An ACARS CALL uplink has been received Activate the ACARS MCDU Operation and select
” ACARS REC MSG ” Pg.
ACARS MESSAGE An ACARS UPLINK has been received Activate the ACARS MCDU Operation and select
” ACARS REC MSG ” Pg.
VHF3 VOICE VHF 3 set in VOICE mode Use TFR switch on RCP to select ACARS mode
ACARS NO COM ACARS link not possible. Out of ground station range Check VHF 3

Indications in the cockpit

Situation Indication on MCDU Indication on the MCDU display Indication on RCP

No link to ground station NO COMM, MSG NOT GEN ACARS NO COM ACARS in the ”ACTIVE” WINDOW
ACARS not controlling VHF 3 VOICE MODE, MSG NOT GEN VHF3 VOICE ACARS in the ”STANDBY” WINDOW
ACARS MU fault ACARS not visable on MENU page COM − ACARS FAULT −−−−− in the ”ACTIVE” WINDOW
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Sep 22, 2006 20/ACARS MSGs/L2 Page 87

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

MCDU MENU-ACARS ERROR LOG

Access to the ACARS ERROR LOG page is as following:
ACARS PREFLIGHT MENU:
⇒ MISC,
⇒ MAINT,
⇒ STATUS,
⇒ ERROR LOG.

ACARS Error Log

CLASS 1, 2 and 3 FAULTS:
The failure with the highest priority occurs at first.
 LSK2 L : Failure description (LEG, DATE, UTC)
 LSK3 L : Fault Message Text
 LSK5 L: Troubleshooting Message Text
 LSK5 R: Failure-Count

Ground Faults:
This shows existing and intermitted faults, sensed on ground.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Okt 13, 2006 21/ACARS Test/L2 Page 88

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COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS PREFLT MENU 2/2 ACARS PREFLT MENU 1/2

DEPARTURE FLT
CLEARENCE > < INIT + DEP ATIS > MENU
PUSHBACK
REQUEST > < OFP DATA WX/ATIS > <FMC (ACT)
OTHER TAXI
< REQUESTS REQUEST > < FUEL FLIGHTLOG > <ACARS
CREW
< DE-ICING MEALS > < SIGN DELAY > <ACMS
DATA GROUND
< TELEX ENTRY > < TELEX HANDLING >
RECEIVED RECEIVED
< MISC MESSAGES> < MISC MESSAGES>

INIT RTE CLB BRT

ACARS MAINTENANCE REF CRZ DES

ACARS MISC MENU LEGS DEP HOLD PROG EXEC

< PARTNUMBERS ARR
DATA
< STATUS
< FREQUENCY VHF
STATISTICS > < TEST
OOOI SATELLITE < COMM
< STATUS STATISTICS >
< APM
RETURN TO
PARAMETER < ACARS MENU
DISPLAY >
RETURN TO
< ACARS MENU MAINT>

ACARS STATUS

<ERROR LOG
FOR TRAINING PURPOSES ONLY!

ACARS ERROR LOG HFDR1 >

CLASS 1 AND 2 FAULTS <RCV 429 DATA HFDR2 >
ACARS ERROR LOG 1/3 <FAULTS 3 <TX 429 DATA
CLASS 3
CLASS 1 AND 2 FAULTS <FAULTS 0 <LRU
AC REG=. D−ABIB GROUND
LEG DATE UTC ATA CLS <FAULTS 0 <DISCRETES
008 FEB 03 1424 24000 1 RETURN TO
POWER SUPPLY INTERRUPT < ACARS MENU
ACARS PWR IN FLT
ADDR COUNT RETURN TO
GECE: 007E* 1 <STATUS MENU PRINT>
RETURN TO
<ERROR MENU PRINT>

Figure 51 MCDU Pages Error LOG

FRA US/T NM Okt 13, 2006 21/ACARS Test/L2 Page 89
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COMMUNICATIONS B737−300/400/500
ACARS
23−27
ACARS FREQUENCY PAGE, TEST PAGE
This page shows the active ACARS frequency - default is Europe with the
frequency of 131.725 MHz.
Any other ACARS frequency is selectable by LSK.
The character before the frequency data means:
 A: − automatic selection
 M: − manually selected
 S: − selected by acars ground station
 D: − selected by acars ground station
The message AUTO/MAN FREQ MISMATCH appears in the Scratch Pad,
when the manually selected area doesn’t agree with the FMC PPOS.
In case of no PPOS available, the following message shows:
 NO LAT/LON, USE MAN FREQ

TEST PAGE
On Maintenance Page you get access to the TEST page.
On the associated RCP you can see the message ACARS in the active
frequency window.
That means the ACARS MU is connected to the VHF-3 transceiver.
 LINK TEST:
This function activates a Downlink (DL) to test the link to a ground station.
Push LSK 1L to activate the test. During the test procedure, TEST is
indicated. If the link is possible, PASS is shown. If there is no connection to
a ground station, FAIL is shown. The message INITIATE appears about 5 s
after the end of the test.
FOR TRAINING PURPOSES ONLY!

 PRINTER TEST:
This function activates a test printout on the printer.
 COM AUDIT:
this function can be switched ON and OFF. If the function is ON, a status
report is printed, when a DL or a Uplink (UL) is activated.
 MCDU TEST:
This function shows a test indication on the MCDU screen.
 RAM TEST:
This function activates internal RAM testing. Indication is PASS or FAIL.

FRA US/T NM Okt 13, 2006 21/ACARS Test/L2 Page 90

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

MENU
<FMC (ACT)
<ACARS
ACARS MISC
<ACMS
DATA
< FREQUENCY VHF ACARS PREFLT MENU 1/2
STATISTICS > FLT
OOOI SATELLITE
STATISTICS > < INIT + DEP ATIS >
< STATUS
< OFP DATA WX/ATIS >
PARAMETER
DISPLAY > < FUEL FLIGHTLOG >
RETURN TO DELAY > INIT BRT
< SIGN REF RTE CLB CRZ DES
< ACARS MENU MAINT> GROUND
< TELEX HANDLING >
RECEIVED MENU LEGS DEP HOLD PROG EXEC
< MISC MESSAGES> ARR

ACARS DATA FREQ ACARS PREFLT MENU 2/2 1

A131.725 DEPARTURE
< EUR/SITA EUR/ARINC > CLEARENCE >
PUSHBACK
< RUSSIA OTHER REQUEST > ACARS TEST 1/2
TAXI
< REQUESTS REQUEST > VHF LINK SAT LINK
CREW
< DE-ICING MEALS > < INITIATE INACTIVE
DATA PRINTER HF LINK
< TELEX ENTRY > < INITIATE NO HF
RETURN TO RECEIVED APM SDU 1
< ACARS MENU AUTOMATIC < MISC MESSAGES> < INITIATE NO TEST
RAM TEST SDU 2
< INITIATE NO TEST
HFDR 1
< COM AUDIT
AIRPLANES WITH RETURN TO NO TEST
HFDR 2
DATALINK MODE 2 ACTIVE < ACARS MENU NO TEST
FOR TRAINING PURPOSES ONLY!

ACARS DATA FREQ ACARS MAINTENANCE ACARS TEST 2/2

136.975
FMC
<PARTNUMBERS < INITIATE
ACMS ACMS
<STATUS NO TEST NO TEST
CABIN 1 CABIN 1
OPERATING IN VDLM 2 1 <TEST NO LRU NO TEST
<COMM
<APM
RETURN TO RETURN TO
RETURN TO
< ACARS MENU < ACARS MENU < ACARS MENU

Figure 52 MCDU PAGES - ACARS DATA FREQUENCY

FRA US/T NM Okt 13, 2006 21/ACARS Test/L2 Page 91
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COMMUNICATIONS B737−300/400/500
ACARS
23−27
ACARS MAINTENANCE
On Maintenance Page you get access to the following functions:
 PARTNUMBERS−,
 STATUS−,
 COMM Status−and
 TEST−Pages.
ACARS PARTNUMBER
This page shows all part numbers of the system (hardware and software) .
The software partnumbers actually in the system and the information on the
diskettes must be the same.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Okt 13, 2006 21/ACARS Test/L2 Page 92

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS MAINTENANCE

ACARS PARTNUMBERS <PARTNUMBERS

MU HW P/N MU S/N <STATUS
965−0758−002 2633
CORE SW P/N REV <TEST
998−2145−518 <COMM
APP SW P/N REV
998−2141−517
DB P/N RETURN TO
DLH-B737C-21 < ACARS MENU
RETURN TO
< ACARS MENU PRINT >
FOR TRAINING PURPOSES ONLY!

Figure 53 MCDU Pages - ACARS Partnumbers

FRA US/T NM Okt 13, 2006 21/ACARS Test/L2 Page 93
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COMMUNICATIONS B737−300/400/500
ACARS
23−27
MU RESET
On the ACARS MAINTENANCE PAGE, you have to insert a special password
and press LSK 6R.
This will show the ACARS DEBUG page 1.
On page 2, you will find the box-prompts MU RESET.
If the word RESET MU is entered in SP and LSK 6R is pressed, a COLD
START is activated - system reinitialization!

ATTENTION: Pressing the test knob at the MU initiates also a MU-coldstart.

This resets all data the MU is presently working with, including
data entered via the MCDU.
Before you carry out the MU RESET, note the QTY BEFORE
fuel data on the ACARS REFUELING REPORT PAGE.
After MU RESET, enter this value into the scratch-pad
(without decimal-point) and press the LSK 1R on the MCDU.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Okt 13, 2006 21/ACARS Test/L2 Page 94

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COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS MAINTENANCE ACARS PREFLT MENU 1/2

FLT
<PARTNUMBERS < INIT + DEP ATIS >
<STATUS < OFP DATA WX/ATIS >
<TEST < FUEL FLIGHTLOG >
<COMM < SIGN DELAY >
< APM < TELEX
GROUND
RETURN TO HANDLING >
RECEIVED
< ACARS MENU < MISC MESSAGES>
SAM

TYPE ’SAM’ INTO

THE SCRATCHPAD
AND PRESS LSK 6R

ACARS DEBUG 1/3 ACARS FUEL REPORT

VOLUME UPLING QTY BFOR
<VHF FMC> ( ) 3.6
UNITS UPLINK SUPP
<MEMORY DUMP SPARE 2> LT −−−− −
DENSITY FOB
<PRINTER ACMS> 0.800 3.7
<MCDU SPARE 5> SUPPLIER FUEL DIFF
−−−− −
CABIN 1> FUEL DEST
A PRINT >
RETURN TO CABIN 2> RETURN TO REPORT
< MAINT MENU < ACARS MENU SEND
FOR TRAINING PURPOSES ONLY!

ACARS DEBUG 2/3

< MSG
< BIT
< VERSION
< OAT
MU RESET
RETURN TO
TYPE ’RESET MU’ INTO < MAINT MENU
THE SCRATCHPAD AND
PRESS LSK 6R RESET MU

Figure 54 MCDU Pages - MU RESET, ACARS FUEL REPORT

FRA US/T NM Okt 13, 2006 21/ACARS Test/L2 Page 95
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS MU FRONTPANEL TEST

CONFIG-1
After installation, correct operation of the ACARS MU can be checked by using TEST-PUSHBUTTON
the following controls located on the MU frontface:

PASS/FAULT Indicator Lights

In normal operation, the lights indicate the actual status of the ACARS MU.
In test mode, after a 3s indicator light test, the lights indicate the test result.
MK II
7 Segment LED
If a test is activated and a failure is detected, the LED shows a fault code. MU PASS

Examples:
 3: A/C registration missed (the MU did not receive the A/C registration)
CMU HW FAIL

LOAD SW
 2: A/C type mismatch (the A/C type defined in software is different to the XFER
pin program information) BUSY
XFER
 1: Bad H/W part number (the MU partnumber and the pin program COMP
information is different) XFER
FAIL

TEST pushbutton APM FAIL

When pressing the test pushbutton switch:

 a ACARS MU ”Cold Start” is initiated.
 the LRU PASS and FAULT lights come on for 3s approximately to indicate
correct operation.
 the red FAULT light goes off to indicate, that no fault is present.
If the red FAULT light remains on and the green light goes off, the system is
faulty and shows a fault code on the LED.
FOR TRAINING PURPOSES ONLY!

CONFIG-2 ACARS MU
Pressing the testbutton will first illuminate all LEDs, then all LEDs will (CONFIG-1)
extinguish and thereafter, according to cmu-status, the green MU-P ASS LED
will illuminate. In case of test failed, the red HW-FAIL LED illuminates.
CAUTION: PRESSING THE TEST KNOB AT THE MU INITIATES A
MU-COLDSTART! THIS RESETS ALL DATA THE MU IS ACARS MU
PRESENTLY WORKING WITH, INCLUDING DATA ENTERED (CONFIG-2)
VIA THE MCDU!!! (ADDITIONAL PROGRAMMING IS LOST!) .
Figure 55 ACARS MU Frontpanel Test
ATTENTION: See also ACARS MU RESET!!!

FRA US/T NM Nov 21, 2006 23/ACARS FRONT−Test/L2 Page 96

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COMMUNICATIONS B737−300/400/500
ACARS
23−27

MAINTENANCE TIPS / TROUBLESHOOTING

MCDU Message: NO COMM
 Description: The message NO COMM appears at the scratchpad on the
MCDU.
 Status:
A display of NO COMM does not necessarily indicate an aircraft failure.
It does indicate that the data-link air/ground network was not completed.
This can be the result of ground station problems or aircraft failures.
The ACARS transmits over the VHF-3 system.
If this system is inoperative, or the VHF path between the airplane and the
ground station is blocked, the system will go NO COMM.
 Att. Maint.:
− Perform a CB-reset.
− Perform a LINK test at the ACARS test page.
− Check the frequency at the ACARS frequency page.
Make sure that ACARS is set to the correct data link frequency
(Europe: 131,725 Mc) .
− Set ACARS in the VOICE mode.
At the standby window of the RCP appears ACARS and at the
scratchpad of the MCDU appears ACARS VOICE.
Check the quality of the voice-connection with the ground operator.
− Perform a ACARS MU RESET at the DEBUG Page 2/2.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Nov 21, 2006 23/ACARS FRONT−Test/L2 Page 97

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COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS MU - DATA LOAD

The task of the procedure is to install the ACARS software into the
acars-management unit.
1. Select ACARS position on the ADL selection panel.
2. Insert the diskette with the ACARS customer database into the ADL.
3. Make sure the RDY light comes on approximately five seconds.
4. Make sure the PROG light comes on approximately three seconds after the
RDY light goes on.
5. Make sure the COMP light comes on. This is an indication that the software
is installed.
Set the selector switch to NORMAL position on the ADL selection panel.
Push the EJECT button on the data loader. Remove the diskette.
ATTENTION: Make sure the software part-number on the ACARS
maintenance page is correct, that means this P/N agree with
the P/N at the diskette.
FOR TRAINING PURPOSES ONLY!

DISC - LABEL

FRA US/T NM Sep 22, 2006 24/ACARS Data−Load/L2 Page 98

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COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS-MU (CONFIG 1)
NORM
ACMS FMC

INOP INOP ALTERNATE WAY OF DATALOADING

IF AIRBORNE DATA LOADER,
DFDAU INOP DATALOADER SELECTPANEL IS NOT
ACARS INSTALLED OR INOP.

PROG CHNG COMP RDY XFER R/W HRDW

MK II
MU PASS

CMU ACARS MU
HW FAIL

LOAD SW
PROG DATA TRANSFER IN PROGRESS
CHNG DISK CHANGE IS REQUIRED XFER
COMP DATA TRANSFER IS COMPLETE BUSY
RDY UNIT READY FOR OPERATION XFER
XFER DATA TRANSFER FAILURE COMP
R/W UNABLE TO ACCESS DISK DATA XFER
HRDW SYSTEM TEST FAILURE FAIL

ADL DOOR OPEN

AIRPLANES WITH AIRBORNE APM FAIL
DATA LOADER
AIRBORNE DATA LOADER (ADL)
OR AIRPLANES WITHOUT
FOR TRAINING PURPOSES ONLY!

AIRBORNE
PORTABLE DATA LOADER (ADL)
DATA LOADER

D1907
DATA TRANSFER UNIT
RECEPTACLE−FMCS

PORTABLE DATA LOADER RECEPTACLE SELECTOR PANEL FOR PORTABLE

(COCKPIT LH ABOVE OBS. SEAT)
DATA LOADER ACARS-MU (CONFIG 2)
Figure 56 ACARS - Data Load
FRA US/T NM Sep 22, 2006 24/ACARS Data−Load/L2 Page 99
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS SYSTEM - VERIFY PARTNUMBERS

After data loading is accomplished, you must verify wether the just loaded
software is now active in the ACARS or not.
Therefor you have to show up the ACARS PARTNUMBER page.
Access to the ACARS PARTNUMBER page is as following:
ACARS PREFLIGHT MENU:
 ⇒ MISC,
 ⇒ MAINT,
 ⇒ PARTNUMBER

ACARS MAINTENANCE
On Maintenance Page you get access to the following functions:
 PARTNUMBERS−,
 STATUS−,
 COMM Status− and
 TEST−Pages.

ACARS PARTNUMBER
This page shows all part numbers of the system (hardware and software) .
The software partnumbers actually in the system and the information on the
diskettes must be the same.
FOR TRAINING PURPOSES ONLY!

FRA US/T NM Sep 22, 2006 24/ACARS Data−Load/L2 Page 100

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
ACARS
23−27

ACARS PREFLT MENU 2/2 ACARS PREFLT MENU 1/2

DEPARTURE FLT
CLEARENCE > < INIT + DEP ATIS > MENU
PUSHBACK
REQUEST > < OFP DATA WX/ATIS > <FMC (ACT)
OTHER TAXI
< REQUESTS REQUEST > < FUEL FLIGHTLOG > <ACARS
CREW
< DE-ICING MEALS > < SIGN DELAY > <ACMS
DATA GROUND
< TELEX ENTRY > < TELEX HANDLING >
RECEIVED RECEIVED
< MISC MESSAGES> < MISC MESSAGES>

INIT RTE CLB BRT

REF CRZ DES

ACARS MISC MENU LEGS DEP HOLD PROG EXEC

ACARS MAINTENANCE ARR
DATA
< FREQUENCY VHF < PARTNUMBERS
STATISTICS >
OOOI SATELLITE < STATUS
< STATUS STATISTICS > < TEST
PARAMETER
< COMM
DISPLAY > < APM
RETURN TO RETURN TO
< ACARS MENU MAINT> < ACARS MENU
FOR TRAINING PURPOSES ONLY!

ACARS PARTNUMBERS
MU HW P/N MU S/N
965−0758−002 2633
CORE SW P/N REV
998−2145−518
APP SW P/N REV
998−2141−517
DB P/N
DLH-B737C-21
RETURN TO
< ACARS MENU PRINT >

Figure 57 MCDU Pages: ACARS Partnumbers

FRA US/T NM Sep 22, 2006 24/ACARS Data−Load/L2 Page 101
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
COCKPIT VOICE RECORDER
23−71

23−71 COCKPIT VOICE RECORDER

COCKPIT VOICE RECORDER PRESENTATION
The voice recorder system records and preserves a continuing record of the Operating power for the voice recorder system is 115 volts, 400 Hz AC
latest 30 minutes of flight crew communications and conversation. obtained from the unswitchable electronics bus through the VOICE
The voice recorder system has four inputs for simultaneous recording of all RECORDER circuit breaker on the P18 panel.
communications in the flight compartment on four track tape.
System Function and Power Supply
 Channel one receives audio from the first observer’s audio selector panel,
As soon as power is applied, the voice recorder system records the latest 30
 channel two receives audio from the first officer’s audio selector panel, minutes of communications and conversation in the flight compartment.
 channel three receives audio from the captain’s audio selector panel and The system is in operation whenever 115−volt AC power is applied to AC bus
 channel four audio is taken from a microphone in the voice recorder control No. 1.
panel. Communications and interphone audio from the first observer’s, the first
The voice recorder system consists of: officer’s and the captain’s audio selector panels is applied to channel 1 through
 a recorder unit installed on the right side of the airplane in the aft cargo 3 respectively of the voice recorder.
compartment; Conversation in the flight compartment is picked up and amplified by the
 a control panel installed in the pilots’ overhead panel P5; interconnecting microphone and preamplifier in the voice recorder control panel and applied to
wiring; channel 4.
 and relay contacts in the landing gear accessory unit Module M338. The playback head and monitor amplifier are used to monitor information
recorded on all tracks of the tape.
An erase head in the recorder automatically erases previously recorded
information prior to recording. The audio output of the monitor amplifier is available at the MONITOR jack on
the front panel of the voice recorder and at the HEADSET jack on the voice
A 30−minute length of closed loop magnetic tape provides a record of the
recorder control panel.
previous 30 minutes of conversation.
This audio is supplied to the test meter on the voice recorder control panel.
An internal monitoring circuit ensures proper operation of the recording
mechanism and circuits. Self test for Fairchild Voice Recorder Model A100
FOR TRAINING PURPOSES ONLY!

Audible and visible indications derived from the monitoring circuits are Press and hold the TEST pushbutton for at least 5 seconds:
presented at a meter and a jack on the control panel when the test switch on
 the test module applies a 600−Hz signal to each channel in sequence,
the control panel is operated.
thereby testing all channels.
The entire tape may be erased after the airplane has landed and the parking
 If they are functioning properly, the control panel meter reads in the green
brake has been set.
area and a modulated sound is present at both jacks.
An ULB (Underwater Locating Beacon) is installed on the front panel of the
The bulk erase circuits erase all audio on the recorder tape within ten seconds
voice recorder.
after the ERASE switch on the control panel is released.
The ULB is an acoustic beacon that energizes when it is immersed in water,
The bulk erase circuits will function only when the airplane is on the ground and
thereby assisting to locate the recorder in case of an accident over the ocean
the parking brake is set because the control circuit must be completed through
or other body of water.
relay K4 in the landing gear accessory unit module.

FRA US/T NM Sep 21, 2006 25/CVR DESCR/L2 Page 102

Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
COCKPIT VOICE RECORDER
23−71

VOICE
RECORDER
A
115V AC RECORDING
UNSWITCHED CHANNEL 1 AMPLIFIERS
OBSERVER
ELECTRONICS
BUS FLIGHT ERASE
INTERPHONE CHANNEL 2
P18−2 SYSTEM FIRST OFF
(INCLUDING HOT
TEST ERASE
MIKROPHONE) CHANNEL 3 RECORDING HEADS
CAPTAIN
HEADSET
COCKPIT VOICE RECORDER
CHANNEL 4
PREAMP AREA MIC BULK
PLAYBACK ERASE
MIC TEST
TEST METER MONITOR
METER AMPLIFIER
TEST TAPE TRANSPORT
(PROTECTED)

MONITOR ALL
JACK 1 TEST
TEST SWITCHES MODULE
ERASE (OPTIONAL) 2 (600 Hz)
3 MONITOR
4 JACK

POWER BULK
SUPPLY ERASE
VOICE RECORDER
CONTROL PANEL TO
INTERNAL
CIRCUITS
FOR TRAINING PURPOSES ONLY!

VOICE RECORDER UINIT

A

PARKING BRAKE SET

PLANE ON GROUND

LANDING GEAR LOGIC SHELF E11

Figure 58 Voice Recorder-Description
FRA US/T NM Sep 21, 2006 25/CVR DESCR/L2 Page 103
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
COCKPIT VOICE RECORDER
23−71

VOICE RECORDER-COMPONENT LOCATION OVERHEAD

PANEL P5

CENTER P6

LOAD CONTROL

TEST ERASE
FOR TRAINING PURPOSES ONLY!

HEADSET
COCKPIT VOICE RECORDER 600 OHMS

CONTROL UNIT

Figure 59 Voice Recorder-Locations Cockpit

FRA US/T NM Sep 21, 2006 26/CVR COMP−LOC/L2 Page 104
Lufthansa Technical Training
COMMUNICATIONS B737−300/400/500
COCKPIT VOICE RECORDER
23−71

AFT CARGO
HEADSET DOOR
JACK

TEST VOICE RECORDER

1
MONITOR
600 OHMS 2

3 TEST
SWITCHES
4
FOR TRAINING PURPOSES ONLY!

ALL

UNDERWATER
LOCATING
DEVICE (ULD)
MODIFICATIONS UNDERWATER
LOCATOR
FAIRCHILD VOICE BEACON (ULB) FAIRCHILD VOICE
RECORDER MODEL A100 RECORDER MODEL A100A
Figure 60 Voice Recorder-Locations other Areas
FRA US/T NM Sep 21, 2006 26/CVR COMP−LOC/L2 Page 105
 B737-3_23_B1

TABLE OF CONTENTS
ATA 23 COMMUNICATIONS . . . . . . . . . . . . . . . . . . 1 HF SYSTEM - DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
HF SYSTEM - COMPONENT LOCATION . . . . . . . . . . . . . . . . . . . . . . . 58
23−00 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 CALSEL-SYSTEM DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
AUDIO COMPONENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 HF SYSTEM-COMPONENT DESCRIPTION . . . . . . . . . . . . . . . . . . . . . 62
AUDIO CONTROL PANEL GENERAL DESCRIPTION . . . . . . . . . . . . 6 HF TUNING SYSTEM FUNCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
23−51 FLIGHT INTERPHONE SYSTEM . . . . . . . . . . . . . . . . . . . . . . 10 HF SYSTEM FUNCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
SYSTEM PRESENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 HF SYSTEM - BITE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
OXYGEN MASK MICROPHONES PRESENTATION . . . . . . . . . . . . . . 14 23−28 SELCAL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
POWER SUPPLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 SELCAL SYSTEM PRESENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
PRESENTATION OF PTT-SWITCHES . . . . . . . . . . . . . . . . . . . . . . . . . . 18 SELCAL DECODER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
FLIGHT INTERPHONE - LOCATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 20 23−27 ACARS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
23−41 SERVICE INTERPHONE SYSTEM . . . . . . . . . . . . . . . . . . . . . 22 ACARS-INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 ACARS-GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
SERVICE INTERPHONE - LOCATION . . . . . . . . . . . . . . . . . . . . . . . . . . 24 ACARS SYSTEM - INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
23−43 FLT/GND CREW CALL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 ACARS - COMPONENT LOCATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
GENERAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 MESSAGE PRESENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
CALL SYSTEM LOCATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 MCDU MENU-ACARS ERROR LOG . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
ACARS MU FRONTPANEL TEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
23−31 PASSENGER ADDRESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
MAINTENANCE TIPS / TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . 97
PASSENGER ADDRESS- INTRODUCTION . . . . . . . . . . . . . . . . . . . . . 32
ACARS MU - DATA LOAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
PA-SYSTEM ARCHITECTURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
ACARS SYSTEM - VERIFY PARTNUMBERS . . . . . . . . . . . . . . . . . . . . 100
PA COMPONENTS - LOCATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
PASSENGER ADDRESS SYSTEM - SPEAKERS . . . . . . . . . . . . . . . . 38 23−71 COCKPIT VOICE RECORDER . . . . . . . . . . . . . . . . . . . . . . . . 102
TAPE REPRODUCER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 COCKPIT VOICE RECORDER PRESENTATION . . . . . . . . . . . . . . . . . 102
PA-AMPLIFIER/TEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 VOICE RECORDER-COMPONENT LOCATION . . . . . . . . . . . . . . . . . . 104
23−21 VERY HIGH FREQUENCY SYSTEM . . . . . . . . . . . . . . . . . . . 44
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
23−10 SPEECH COMMUNICATION . . . . . . . . . . . . . . . . . . . . . . . . . . 48
RADIO COMMUNICATION PANEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
23−21 VHF-COMMUNICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
SYSTEM DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
VHF SYSTEM - LOCATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
VHF 700 / 900 - BITE DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
23−11 HF-COMMUNICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Page i
 B737-3_23_B1

TABLE OF FIGURES
Figure 1 AUDIO INTEGRATING - GENERAL . . . . . . . . . . . . . . . . 3 Figure 36 CALSEL-Presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Figure 2 Audio Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 37 HF Freq.-Radio Control Panel (RCP) . . . . . . . . . . . . . . . 63
Figure 3 AUDIO CONTROL PANEL Introduction (CONFIG 1) . . 7 Figure 38 HF System-Components . . . . . . . . . . . . . . . . . . . . . . . . . 65
Figure 4 AUDIO CONTROL PANEL - (CONFIG 2) . . . . . . . . . . . . 9 Figure 39 HF-Functional Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Figure 5 Flight Interphone-Architecture . . . . . . . . . . . . . . . . . . . . . . 11 Figure 40 HF System-Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Figure 6 Flight Interphone Activation on ACP . . . . . . . . . . . . . . . . . 13 Figure 41 HF System-BITE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Figure 7 Oxygen Mask Mike Operation . . . . . . . . . . . . . . . . . . . . . . 15 Figure 42 SELCAL-System Presentation . . . . . . . . . . . . . . . . . . . . . 73
Figure 8 Flight Interphone-Power Supply . . . . . . . . . . . . . . . . . . . . 17 Figure 43 SELCAL-System Function (Config. 1) . . . . . . . . . . . . . . 74
Figure 9 Flight Interphone-PTT Function . . . . . . . . . . . . . . . . . . . . . 19 Figure 44 SELCAL-System Function (Config. 2) . . . . . . . . . . . . . . 75
Figure 10 FLT Interphone - FLT Deck Location . . . . . . . . . . . . . . . 20 Figure 45 SELCAL System-Component Location . . . . . . . . . . . . . 77
Figure 11 FLT Interphone-Component Location (other Areas) . . . 21 Figure 46 ACARS-Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Figure 12 Service Interphone-Schematic . . . . . . . . . . . . . . . . . . . . . 23 Figure 47 ACARS - General Description . . . . . . . . . . . . . . . . . . . . . 81
Figure 13 Service Interphone/Component Location . . . . . . . . . . . . 24 Figure 48 ACARS Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Figure 14 SERVICE INTERPHONE-JACKS LOCATION . . . . . . . 25 Figure 49 ACARS-Component Location Cockpit . . . . . . . . . . . . . . 84
Figure 15 Call System/Config. 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Figure 50 ACARS-Component Location Equipment Rack . . . . . . 85
Figure 16 Call Systems/Config. 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Figure 51 MCDU Pages Error LOG . . . . . . . . . . . . . . . . . . . . . . . . . 89
Figure 17 Call Systems/Component Location . . . . . . . . . . . . . . . . . 30 Figure 52 MCDU PAGES - ACARS DATA FREQUENCY . . . . . . . 91
Figure 18 Call Systems/Component Location . . . . . . . . . . . . . . . . . 31 Figure 53 MCDU Pages - ACARS Partnumbers . . . . . . . . . . . . . . 93
Figure 19 PA-General Description . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Figure 54 MCDU Pages - MU RESET, ACARS FUEL REPORT . 95
Figure 20 PA-System Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Figure 55 ACARS MU Frontpanel Test . . . . . . . . . . . . . . . . . . . . . . 96
Figure 21 PA - Component Location 1 . . . . . . . . . . . . . . . . . . . . . . . 36 Figure 56 ACARS - Data Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Figure 22 PA - Component Location 2 . . . . . . . . . . . . . . . . . . . . . . . 37 Figure 57 MCDU Pages: ACARS Partnumbers . . . . . . . . . . . . . . . 101
Figure 23 PA-Speakers Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Figure 58 Voice Recorder-Description . . . . . . . . . . . . . . . . . . . . . . . 103
Figure 24 PA/Tape Reproducer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Figure 59 Voice Recorder-Locations Cockpit . . . . . . . . . . . . . . . . . 104
Figure 25 PA Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Figure 60 Voice Recorder-Locations other Areas . . . . . . . . . . . . . . 105
Figure 26 VHF-General Description, Conf. 1 . . . . . . . . . . . . . . . . . 45
Figure 27 VHF - General Description Conf. 2 . . . . . . . . . . . . . . . . 47
Figure 28 Radio Communication Panel . . . . . . . . . . . . . . . . . . . . . . 49
Figure 29 VHF-700 Collins System Architecture . . . . . . . . . . . . . . 51
Figure 30 VHF - Antenna Locations . . . . . . . . . . . . . . . . . . . . . . . . . 52
Figure 31 VHF 700 Collins Locations . . . . . . . . . . . . . . . . . . . . . . . . 53
Figure 32 VHF 900 - TRANSCEIVER BITE . . . . . . . . . . . . . . . . . . 55
Figure 33 HF System-Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Figure 34 HF System-Component Location (Cockpit) . . . . . . . . . . 58
Figure 35 HF System-Component Location (other Areas) . . . . . . 59

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