1.
Introduction to RTC
Q1: What is RTC, and what does it stand for?
A1:
RTC (Réseau Téléphonique Commuté, also known as PSTN - Public Switched Telephone
Network) is the traditional circuit-switched telephone network used for voice
communication. It allows users to make calls using fixed-line telephones by establishing a
dedicated connection between the caller and receiver for the duration of the call.
2. Historical Evolution of RTC
Q2: What are the key historical milestones of the RTC network?
A2:
1794: Claude Chappe developed the optical telegraph for long-distance
communication (Paris-Lille).
1844: Expansion of the telegraph system to 5,000 km of network.
1877: Alexander Graham Bell invented the electric telephone, capable of
transmitting voice signals.
20th Century: Widespread deployment of telephone networks using copper wire and
electromechanical switching systems.
21st Century: RTC networks are gradually being phased out in favor of VoIP (Voice
over IP) and fiber-optic networks.
3. Basic Principle of RTC
Q3: How does RTC work?
A3:
RTC operates using circuit-switching, meaning a dedicated communication path is
established between two users for the entire duration of a call. The process involves:
1. Call setup – A connection is established through switching centers.
2. Data transmission – Voice signals are transmitted as analog or digital signals.
3. Call termination – The circuit is released after the conversation ends.
4. Components of RTC Network
Q4: What are the main components of an RTC network?
A4:
1. Subscriber terminals – Telephones, fax machines, or modems.
2. Local loops – The physical copper line connecting the user to the exchange.
3. Switching centers – Nodes that establish call connections.
4. Trunk lines – High-capacity links connecting switching centers.
5. International gateways – Interfaces for cross-border communication.
5. Architecture of RTC Network
Q5: How is the RTC network structured?
A5:
The RTC network consists of multiple hierarchical components:
Local Exchange (LE): Connects individual users to the network.
Tandem Exchange: Connects multiple local exchanges.
Transit Exchange: Handles long-distance calls.
International Exchange: Routes calls between countries.
6. RTC Call Establishment
Q6: What are the steps in establishing a call in an RTC network?
A6:
1. User dials a number – The digits are sent to the local exchange.
2. Call setup – The exchange finds an available route to the recipient.
3. Connection establishment – The receiver's phone rings.
4. Conversation phase – The dedicated circuit remains active.
5. Call termination – When the call ends, the circuit is released.
7. RTC Signaling and Switching
Q7: What is the role of signaling in RTC?
A7:
Signaling in RTC is responsible for:
Establishing, maintaining, and terminating calls.
Call routing using dialed numbers.
Billing and charging users based on call duration.
Types of signaling used in RTC:
1. In-band signaling – Uses the same channel as voice (e.g., DTMF tones).
2. Out-of-band signaling – Uses separate control channels (e.g., SS7).
8. Types of RTC Switching
Q8: What are the different types of switching in RTC?
A8:
1. Manual Switching – Early telephone systems where operators manually connected
calls.
2. Electromechanical Switching – Uses relays and mechanical components to route calls.
3. Electronic Switching – Uses digital technology for faster call routing.
9. RTC Call Routing and Numbering
Q9: How are phone numbers structured in RTC?
A9:
Phone numbers follow the E.164 numbering plan, which includes:
Country Code (CC) – Identifies the country (e.g., +1 for the USA, +33 for France).
National Destination Code (NDC) – Identifies the region or operator.
Subscriber Number (SN) – Unique number for each user.
10. RTC Frequency and Transmission
Q10: What are the frequency ranges used in RTC voice transmission?
A10:
Voice Frequency Band: 300 Hz – 3,400 Hz.
Dial Tone: 440 Hz.
Ringback Tone: 440 Hz (on/off pattern).
Busy Signal: 500ms on, 500ms off at 440 Hz.
11. RTC Network Infrastructure
Q11: What are the different points in the RTC infrastructure?
A11:
Point de concentration (Concentration Point) – Bundles multiple subscriber lines.
Armoire de sous-répartition (Distribution Cabinet) – Manages network distribution.
Répartiteur (Main Distribution Frame) – Connects local loops to exchanges.
NRA (Nœud de Raccordement Abonnés) – Manages large groups of users.
12. RTC vs. VoIP
Q12: What are the differences between RTC and VoIP?
A12:
Feature RTC (PSTN) VoIP (Voice over IP)
Technology Circuit-switched Packet-switched
Transmission Analog/Digital Fully Digital
Cost Higher Lower (internet-based)
Scalability Limited Highly scalable
Quality Stable Dependent on internet quality
Flexibility Limited mobility Can be used anywhere with the internet
13. RTC Taxation and Billing
Q13: How is billing handled in RTC?
A13:
RTC billing is based on:
Call Duration – Measured from connection to disconnection.
Distance – Local vs. long-distance calls.
Time of Day – Peak vs. off-peak rates.
14. RTC Transmission Technologies
Q14: What are the different transmission mediums used in RTC?
A14:
1. Copper Wire (POTS) – Traditional twisted-pair cables.
2. Fiber Optic (FTTH, FTTC) – High-speed voice and data transmission.
3. Microwave Links – Wireless transmission in remote areas.
15. Future of RTC
Q15: What is the future of RTC networks?
A15:
RTC is being replaced by VoIP, fiber optics, and mobile networks.
Many telecom operators are shutting down RTC services due to high maintenance
costs.
Transition to all-IP networks (e.g., VoIP, SIP, 4G/5G).
