--- title: "Milestones in the evolution of telecommunication" subject: "Telecommunications" chapter: 1 key: "semester_8/telecommunications:evolution-of-telecommunication" source: https://www.bctengineer.com/q/semester_8/telecommunications/evolution-of-telecommunication site: BCT Engineering --- # Milestones in the evolution of telecommunication Telecommunications · Chapter 1: Telecommunication Networks - Asked in: 2071 Shrawan, 7 marks; 2069 Chaitra, 8 marks (asked 2 times) - Video: [The Evolution and Future of Telecommunication Technology (12 Minutes)](https://www.youtube.com/watch?v=_jPsNca0sis) — Microlearning Daily - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/telecommunications/evolution-of-telecommunication - Whole chapter: https://www.bctengineer.com/md/semester_8/telecommunications/chapter-1 ## Question Explain the evolution of Telecommunication. Describe briefly the major milestones in the evolution of telecommunication. ## Short answer Major milestones: optical telegraph (1790s), electric telegraph (1837), telephone (1876), manual exchange (1878), Strowger automatic exchange (1892), transistor (1947), SPC electronic exchange (1965), digital switching (1970s), GSM (1991), and 4G/5G mobile broadband. ## Answer Telecommunication evolved gradually: each new system grew out of the limits of the previous one, moving from visual and electrical signalling to voice, then to automatic switching, radio, digital and finally packet/IP and mobile networks. #### Major milestones | Year | Milestone | |---|---| | 1790s | Optical (semaphore) telegraph of Chappe, France | | 1837–44 | Electric telegraph and Morse code (Morse, Cooke & Wheatstone) | | 1866 | Successful transatlantic telegraph cable | | 1876 | Telephone invented by A. G. Bell | | 1878 | First manual telephone exchange, New Haven (USA) | | 1889–92 | Strowger automatic step-by-step exchange (La Porte, 1892) | | 1895–1901 | Marconi's wireless telegraphy; transatlantic radio (1901) | | 1906 | Triode valve (De Forest); amplifiers make long lines possible | | 1920s–30s | Crossbar switch, carrier (FDM) multiplexing, coaxial cable | | 1937 | Pulse code modulation (Reeves) | | 1947 | Transistor invented (Bell Labs) | | 1956 | First transatlantic telephone cable (TAT-1) | | 1962 | Telstar satellite; T1 PCM carrier systems | | 1965 | No. 1 ESS – first stored program control exchange | | 1970 | Low-loss optical fibre (Corning); E10 digital exchange | | 1976 | No. 4 ESS digital toll switch; CCITT SS7 later | | 1979–83 | First cellular networks (1G: NTT, AMPS) | | 1980s | ISDN; TCP/IP adopted on ARPANET (1983) | | 1991 | GSM (2G digital mobile); World Wide Web | | 2001 | 3G (UMTS) | | 2009–10 | 4G LTE | | 2019 | 5G deployment | #### Main trends - **Manual → automatic:** operators replaced by Strowger, crossbar and then computer-controlled (SPC) exchanges. - **Analogue → digital:** PCM, TDM and digital switching gave better quality and integration of voice and data. - **Copper → fibre and radio:** higher bandwidth and lower loss; satellites and microwave for long distance. - **Fixed → mobile:** cellular networks from 1G to 5G. - **Circuit → packet:** Internet, VoIP and all-IP networks. Each milestone increased capacity and quality and lowered cost, which is why telecom is called an evolutionary process. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which list correctly gives the main trends of telecom evolution? A. Manual to automatic, analogue to digital, copper to fibre/radio, fixed to mobile, circuit to packet B. Automatic to manual, digital to analogue, fibre to copper, mobile to fixed C. Circuit to packet, but analogue stays and exchanges stay manual D. Only a change from copper to fibre; the other aspects stayed the same Answer: A. The answer lists these five trends, each raising capacity and quality and lowering cost. (Key point: Trends) 2. Which sequence of inventions is in the correct order? A. Strowger exchange, telephone, No. 1 ESS, transistor B. Telephone (1876), Strowger exchange (1892), transistor (1947), No. 1 ESS (1965) C. Transistor, telephone, No. 1 ESS, Strowger exchange D. Telephone, No. 1 ESS, Strowger exchange, transistor Answer: B. Dates: Bell 1876, Strowger La Porte 1892, transistor 1947, No. 1 ESS 1965. (Key point: Milestone order) 3. Why was the triode valve (1906) important for telecom? A. It allowed digital switching B. It replaced optical fibre C. Amplifiers made long lines possible D. It invented the telephone transmitter Answer: C. The triode amplifier overcame attenuation, making long-distance lines practical. (Key point: Amplification) 4. Which statement about mobile generations is right? A. GSM was the 1G analogue system B. 4G LTE appeared before 3G C. 5G was deployed before 2G D. 1G was analogue cellular (1979-83), GSM 2G came in 1991, followed by 3G, 4G LTE and 5G Answer: D. Cellular began with analogue 1G, then digital GSM (1991), 3G (2001), 4G (2009-10), 5G (2019). (Key point: Mobile) ## Related in Telecommunications - [Evolution of telecommunication and switching systems](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aevolution-telecom-switching) — Telecommunications, chapter 1, asked 3× - [Switching hierarchy and evolution until the telephone](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aswitching-hierarchy-telephone-evolution) — Telecommunications, chapter 1, asked 3× - [Evolution from telegraphy to fiber and wireless](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aevolution-telegraphy-to-fiber) — Telecommunications, chapter 1 - [Digital vs manual switching; evolution in Nepal](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Adigital-vs-manual-nepal-evolution) — Telecommunications, chapter 1 ## Related in other subjects - [Evolution of power systems and milestones](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Aevolution-power-system) — Power System Analysis I, chapter 1