Connectivity
External Connectivity
A port is a connector on a motherboard or on a separate adapter that allows a device to connect to a
computer. Sometimes a motherboard has ports built directly into the motherboard. A technician must be
able to identify these ports readily to ensure that (1) the correct cable plugs into a port and (2) the technician
can troubleshoot problems in the right area.
Many port connections are either male or female. Male ports have metal pins that protrude from the
connector. A male port requires a cable with a female connector. Female ports have holes in the connector
into which the male cable pins are inserted.
Some connectors on integrated motherboards are either D-shell connectors or DIN connectors. A D-shell
connector (sometimes called a D-sub) has more pins or holes on top than on the bottom, so a cable
connected to the D-shell connector can be inserted in only one direction and cannot be accidentally flipped
upside down. Many documents represent a D-shell connector by using the letters DB, a hyphen, and the
number of pins—for example, DB-9, DB-15, or DB-25.
A mini-DIN-6 connector is round with small holes and is normally keyed. When a connector is keyed, the
cable can be inserted only one way. Keyboard and mouse connectors, commonly called PS/2 ports, are
examples of mini-DIN connectors. Today, a keyboard and mouse most often connect to USB ports.
Mouse and Keyboard Ports
Mouse and keyboard ports have traditionally been 6-pin mini-DIN ports that are sometimes called PS/2
ports. Otherwise, USB ports are used for mouse and keyboard connectivity. Many manufacturers color code
the PS/2 mouse port as green and the PS/2 keyboard port as purple or they may put a small diagram of a
keyboard or a mouse by each connector.
Video Ports
A video port is used to connect a display. Video output can be the older method of analog signal (varying
levels, such as seen with an audio signal) or the newer output method of digital signal (1s and 0s). Because
the computer uses all digital signals, sending 1s and 0s is more efficient than having to convert the 1s and 0s
to an analog signal. This is relevant because there are still video ports around that are designed for analog
signals.
Cathode ray tube (CRT) monitors were the big bulky ones that looked like old TV sets that accepted analog
output from computers. Flat panel monitors accept digital signals.
Video Graphics Array (VGA)
The video graphics array (VGA) port was designed for analog output to a CRT monitor. VGA ports are easy to
identify because they have three rows of holes. The female port is sometimes advertised as an HD-15 or DE-
15 port. The VGA cable has a DB-15 male end that attaches to the DE-15 port.
Digital Visual Interface (DVI)
A newer port is a Digital Visual Interface (DVI) port, and it has three rows of square holes. DVI ports are used
to connect flat panel digital displays. Some flat panel monitors can also use the older VGA port. Some video
adapters also enable you to connect a video device (such as a television) that has an S-Video port.
There are several types of DVI connectors. The one used depends on the type of monitor attached. Two
terms used with these DVI connectors are single link and dual link. A single link connection allows video
resolutions up to 1920×1080. With a dual link connection, more pins are available to send more signals, thus
allowing higher resolutions. The two major types of connectors are DVI-D and DVI-I. DVI-D is used for digital
video connectivity only. DVI-I can be used for both digital and analog monitors, and it is the most common.
A less common type is DVI-A, which is used for analog connectivity.
DisplayPort
The DisplayPort developed by VESA (Video Electronics Standards Association) can send and receive video,
audio, or both types of signals simultaneously. The port is designed to primarily output to display devices,
such as computer monitors, televisions, and home theaters. A passive converter can be used to convert to a
single-link DVI or HDMI port. You use an active converter to convert to a dual-link DVI.
To understand why an active converter is needed, you must understand the difference between active and
passive cables. A passive cable is one that does not contain a chip like active cables. Active cables have a
chip that boosts the signals, thus allowing cables to be thinner and to support sending signals further and
faster than passive cables. Active and passive cables are found in computer networks and video systems.
A mini DisplayPort is also available on mobile devices.
Thunderbolt
An updated port that uses some of the DisplayPort technology is the Thunderbolt port. The Thunderbolt
interface was developed by Intel with support from Apple. The Thunderbolt port used on Apple computers
is the same connector as the mini DisplayPort. Thunderbolt 3 will use the USB Type-C connector. In addition
to carrying video signals, a Thunderbolt cable can also be used to carry audio signals and data to external
storage devices.
High-Definition Multimedia Interface (HDMI)
Another upgrade to DVI is High-Definition Multimedia Interface (HDMI), a digital interface that can carry
audio and video over the same cable. HDMI is found on cable TV boxes, televisions, video adapters, laptops,
desktops, and tablets. MiniHDMI, or microHDMI connectors, are used with devices such as cameras, tablets,
and smartphones. Below Table describes the different HDMI ports.
Video Adapters and Converters
DVI-to-HDMI converter VGA-to-DVI converter
DVI-to-VGA converter
Thunderbolt-to-DVI converter
Thunderbolt-to-VGA converter
USB Ports
USB stands for Universal Serial Bus. A USB port allows up to 127 connected devices to transmit at speeds up
to 10Gb/s (10 billion bits per second). Devices that can connect to a USB port include printers, scanners,
mice, keyboards, joysticks, optical drives, tape drives, game pads, cameras, modems, speakers, telephones,
video phones. Additional ports can sometimes be found on the front of a PC case or on the side of a mobile
device.
USB Versions
USB ports and devices come in three versions: 1.0/1.1, 2.0 (Hi-Speed), and 3.0 (SuperSpeed). USB 1.0
operates at speeds of 1.5Mb/s and 12Mb/s; version 2.0 operates at speeds up to 480Mb/s. Version 3.0
transmits data up to 5Gb/s. The 3.0 USB port, which still accepts older devices and cables, is colored blue.
Version 3.1 increases the speed to 10Gb/s, is backward compatible with prior versions, can deliver more
power, and ports are colored teal.
To achieve USB 3.0/1 speeds, however, a 3.0/1 device, 3.0/1 port, and 3.0/1 cable must be used. The version
1 and 2 cables used 4 wires. Version 3 cables use 9 wires. Note that the port is not required to be labeled,
and sometimes looking at the technical specifications for the computer or motherboard is the only way to
determine port speed.
USB Cables
Each USB standard has a maximum cable length:
• Version 1.0/1.1: 9.8 feet, or 3 meters
• Version 2.0: 16.4 feet, or 5 meters
• Version 3.x: 9.8 feet, or 3 meters
USB cables can be longer than these specifications, but the standards are provided to ensure that devices
function properly. Sometimes a USB extender cable is needed.
USB Connectors
USB ports are known as upstream ports and downstream ports. An upstream port is used to connect to a
computer or another hub. A USB device connects to a downstream port. Downstream ports are commonly
known as USB Type-A and USB Type-B. A standard USB cable has a Type-A male connector on one end and
a Type-B male connector on the other end. The port on the computer is a Type-A port. The Type-A connector
inserts into the Type-A port. The Type-B connector attaches to the Type-B port on the USB device.
The USB Type-C connector is the latest connector that will eventually replace the Type-A and Type-B
connectors. Older devices use an adapter and the older cables in order to attach to a Type-C connector.
Many USB 3.x ports are Type-C connectors, but they do not have to be.
USB Hubs
A USB port can have more than one device attached to the port through the use of a USB hub. Many hubs
can operate in two power modes—self-powered and bus-powered—and a hub may have a switch control
that must be set to the appropriate mode. A self-powered hub has an external power supply attached. A
bus-powered hub has no external power supply connected to it. Once USB devices attached to a hub are
tested, the hub’s power supply can be removed and the devices can be retested. If all attached devices work
properly, the hub power supply can be left disconnected.
USB ports have always been able to provide power to unpowered devices, such as flash drives. A charging
USB port is a port designed to be able to provide power- and charge-attached devices. Note that not all USB
devices can be powered on while charging. A sleep-and-charge USB port is one in which the port still provides
power to the device (power to charge the device), even when the computer is powered off. See the
computing device’s specifications to see if a USB port supports this feature.
A smaller USB port used on small devices such as USB hubs, digital cameras, and phones is known as a mini-
USB port. There are several types of smaller USB ports: mini-A, mini-AB, micro-B, and micro-AB. The mini-
/micro-AB ports accept either a mini-/micro-A or a mini-/micro-B cable end.
USB micro-B 3.0 port and cable
Installing Extra USB Ports
Sometimes people want more USB ports and do not want to add another hub or a hub with more ports.
Many motherboards support adding two or more USB ports by using a cable that attaches to motherboard
pins, which is also known as a USB header. The ports mount in an expansion slot space, but they do not take
an expansion slot. Even if the motherboard has such pins, the ports and cable assembly might have to be
purchased separately.
Audio Ports
A sound card converts digital computer signals to sound and sound to digital computer signals. A sound card
is sometimes called an audio card. Sound ports are commonly integrated into the motherboard, but some
people want better sound and so they add a card. The most common sound ports include a port for a
microphone, MP3 player, or other audio device and one or more ports for speakers. The ports can accept
analog or digital signals.
The traditional analog sound ports are 3.5mm. The newer Sony/Phillips Digital interface (S/PDIF) in/out ports
are used to connect to various devices, such as digital audio tape players/recorders, DVD players/recorders,
and external disc players/recorders. There are two main types of S/PDIF connectors: an RCA jack used to
connect a coaxial cable and a fiber-optic port for a TOSLINK cable connection.
IEEE 1394 (FireWire) Ports
The IEEE 1394 standard is a serial technology developed by Apple Inc. Sometimes it is known as FireWire
(Apple), i.Link (Sony), or Lynx (Texas Instruments). IEEE 1394 ports have been more predominant on Apple
computers, but they are also seen on some PCs. Windows and Apple operating systems support the IEEE
1394 standard. Many digital products have an integrated IEEE 1394 port for connecting to a computer. IEEE
1394 devices include camcorders, cameras, printers, storage devices, video conferencing cameras, optical
players and drives, tape drives, film readers, speakers, and scanners.
IEEE 1394 has two data transfer modes: asynchronous and isochronous. The asynchronous mode focuses on
ensuring that data is delivered reliably. Isochronous transfers allow guaranteed bandwidth (which is needed
for audio/video transfers) but do not provide for error correction or retransmission.
Speeds supported are 100, 200, 400, 800, 1200, 1600, and 3200Mb/s. IEEE 1394 devices commonly include
the speed as part of their descriptions or names; for example, a FireWire 400 device transfers at speeds up
to 400Mb/s and a FireWire 800 device up to 800Mb/s. With FireWire, as many as 63 devices (using cable
lengths up to 14 feet) can be connected (daisy-chained). The IEEE 1394 standard supports hot swapping,
plug-and-play, and powering of low-power devices.
An IEEE 1394 cable has 4, 6, or 9 pins. A 4-pin cable/connector does not provide power, so the device must
have its own power source. The 6- and 9-pin connectors do provide power. A 6-pin connector is used on
desktop computers and can provide power to the attached IEEE 1394 device. A 9-pin connector is used to
connect to 800Mb/s devices that are also known as IEEE 1394b devices.
An IEEE 1394 device can connect to a port built into the motherboard, an IEEE 1394 port on an adapter,
another IEEE 1394 device, or a hub. A motherboard might have pins to connect additional IEEE 1394 ports.
IEEE 1394 does not require a PC to operate; two IEEE 1394 devices can communicate via a cable. The IEEE
1394 bus is actually a peer-to-peer standard, meaning that a computer is not needed. Two IEEE 1394–
compliant devices can be connected (for example, a hard drive and a digital camera), and data transfer can
occur across the bus.
IEEE 1394c devices transmit at 800Mb/s, but instead of using a 9-pin connector, they have an RJ-45
connector, such as an Ethernet port. The IEEE 1394d standard uses a fiber connection.
eSATA Ports
SATA (serial AT attachment) is used for connecting storage devices such as hard drives or optical drives.
eSATA can transfer data at 600MB/s. A 7-pin nonpowered external SATA (eSATA) port is used to connect
external storage devices to computers at a maximum of approximately 6.6 feet or 2 meters. An eSATA port
is commonly found on laptops to provide additional storage. If the internal hard drive has crashed, an
external drive connected to an eSATA or USB port could be used to boot and troubleshoot the system.
A variation of the eSATA port is the eSATAp port, which is also known as eSATA/USB or power over eSATA.
This variation can accept eSATA or USB cables and provides power when necessary.
Network Ports
Network ports are used to connect a computer to other computers, including a network server. The most
common type of network port is an Ethernet port. A network cable inserts into the Ethernet port to connect
the computing device to the wired network. A network port or an adapter that has a network port is
commonly called a NIC (network interface card/controller).
Ethernet adapters commonly contain an RJ-45 port that looks like an RJ-11 phone jack, but the RJ-45
connector has 8 conductors instead of 4. UTP (unshielded twisted pair) cable connects to the RJ-45 port so
the computing device can be connected to a wired network. An RJ-45 Ethernet port can also be found on
external storage devices. A storage device could be cabled to the wired network in the same fashion as the
PC.
Modem Ports
A modem connects a computer to a phone line. A modem can be internal or external. An internal modem is
an adapter that has one or two RJ-11 phone jack connectors. An external modem is a separate device that
sits outside the computer and connects to a 9-pin serial port or a USB port. The external modem can also
have one or two RJ-11 connectors. The RJ-11 connectors look like typical phone jacks. With two RJ-11
connectors, one can be used for a telephone and the other has a cable that connects to the wall jack. The
RJ-11 connector labeled Line is for the connection to the wall jack. The RJ-11 connector labeled Phone is for
the connection to the phone. An internal modem with only one RJ-11 connector connects to the wall jack.
Wireless Connectivity for Input Devices
Many input devices, such as keyboards, mice, game pads, touch pads, and headphones, have wireless
connectivity. Technologies used to connect without a cord include infrared, radio, Bluetooth, and near field
communication (NFC). Many computing devices, especially smartphones and other mobile devices, have
cordless connectivity integrated into the device; otherwise, a transceiver is connected to a USB port to allow
connectivity to the computing device.
Summarizes the various wireless technologies used with input and output devices.
