Telecommunication: From the Telegraph to Satellite Communication
In the REET Level 2 Science syllabus, telecommunication is part of the 'Science in Daily Life' section, where questions are asked on the inventions and principles from the telegraph all the way to satellite communication. This page explains each technology in order, along with its inventor, its principle, and how it's used today.
- No direct REET 2024 question, syllabus-based
- Class 6-8 level
- 8 min read
How this topic is asked in REET
We have no verified question related to telecommunication on record from the REET 2024 paper, so we are not showing any fabricated past question here. This note is based entirely on the vocabulary of the 'Application of Science in Daily Life' section of the REET Level 2 Science syllabus, and on NCERT-level understanding. This topic is clearly included in the syllabus, so a direct question based on an inventor, principle, or use could appear in a future paper.
Telegraph and telephone: the first message over a wire
The telegraph is one of the oldest electrical technologies for communicating over distance. American inventor Samuel Morse developed Morse code (a language of dots and dashes) and sent the first public telegraph message in 1844. Telegraph service began in India in the 1850s, and by 1854 a network connecting major cities such as Calcutta, Agra, Bombay and Peshawar was ready.
The invention of the telephone is credited to Alexander Graham Bell, who patented it in 1876. The telephone converts sound (voice) into an electrical signal and sends it over a wire, and converts it back into sound at the other end — this was a major step forward from the telegraph, because now it was not just code that could be sent, but actual voice.
Radio and television: a message without wires
Radio technology sends messages without wires, using electromagnetic waves (radio waves). Italy's Guglielmo Marconi is credited with the commercial development of wireless telegraphy — in 1901 he sent the first transatlantic wireless signal, and for this work he received the Nobel Prize (in Physics) in 1909. It's worth noting that Indian scientist Jagadish Chandra Bose had publicly demonstrated sending a signal without wires in Kolkata in 1895, which came before Marconi's famous demonstrations — though the credit for advancing commercial radio systems goes to Marconi.
As for television, Scottish inventor John Logie Baird built the first working television system in 1925-26, which could send both picture and sound over a distance. Both radio and TV are based on electromagnetic waves, not sound waves — this is an important distinction, because radio waves can travel even through a vacuum, while sound waves need a medium (air, water, etc.) to travel.
Modern telecommunication: satellites, mobile phones, and optical fibre
In satellite communication, artificial satellites placed in Earth's orbit capture signals from one location and relay them to another distant location — this is what makes long-distance phone calls, TV broadcasts and GPS (a system that tells you your position) possible. India's Indian Space Research Organisation (ISRO) operates its INSAT/GSAT series of satellites for tasks such as telecommunication, broadcasting and weather monitoring.
Mobile (cellular) phone networks are also based on radio waves — a city is divided into small 'cell' areas, with mobile towers installed in each area, which connect to phones via radio waves. Optical fibre cable, on the other hand, carries a signal as light (laser) instead of electricity — this is the backbone of high-speed, high-capacity internet data transfer services.
Major inventions and their inventors
| Technology | Inventor/pioneer | Year (approx.) | Principle |
|---|---|---|---|
| Telegraph (Morse code) | Samuel Morse | 1844 | Electrical signal — code sent over a wire |
| Telephone | Alexander Graham Bell | 1876 | Sound ↔ electrical signal — wire |
| Radio (wireless) | Jagadish Chandra Bose (demonstration) / Guglielmo Marconi (commercial development) | 1895 / 1901 | Electromagnetic waves — without wires |
| Television | John Logie Baird | 1925-26 | Electromagnetic waves — picture and sound |
Telephone service began in India in Kolkata in 1881-82.
Essential terms in today's telecommunication
- Optical fibre
- A thin glass/plastic wire through which the signal travels as light; used in the internet and long-distance data communication.
- Satellite communication
- Satellites placed in Earth's orbit relay signals from one location to another — used in long-distance communication, TV broadcasting and GPS.
- Mobile/cellular network
- A system that divides an area into small 'cells' and connects them via radio waves through towers.
- Internet
- The system that links computer networks around the world together, which today relies mainly on optical fibre and satellite communication.
- Bandwidth
- The amount of data that can be sent through a communication medium in a given time — optical fibre has far greater bandwidth than a copper wire.
How to teach this to students
Activity
Make a 'tin-can telephone' using two tin cans and a string, and show how sound vibrations travel along the string — this simply explains the basic idea of a telephone (mechanical transmission of sound), even though a real telephone uses an electrical signal. Loosen the string to show that the sound isn't clear anymore — this also helps explain why the medium needs to be taut.
Teaching aids
Putting up a timeline chart from the telegraph to the internet in class helps children remember the order in which these technologies developed. Showing an old radio set or the inner parts of a mobile phone (SIM card, antenna) also builds interest.
Common misconception
Children often assume that radio/mobile waves are 'sound waves'. Make it clear that these are electromagnetic waves, which can also travel through a vacuum, while actual sound waves need a medium.
Assessment
Have students match inventors with technologies (such as Morse-telegraph, Bell-telephone, Marconi-radio) — this is a quick way to test factual recall.
A trick to remember this
Remember the order — 'wired first, wireless later': telegraph (1844) → telephone (1876) → radio (1895/1901) → TV (1925-26). The two wired technologies came first, then the wireless ones — this order gives you the right direction when a year is asked in the exam. And remember: 'radio waves can't be heard, and they travel even without air' — that's their biggest difference from sound waves.
Practice questions
Question 1
Morse code is used in which technology?
- Aटेलीफोन
- Bरेडियो
- Cटेलीग्राफ
- Dउपग्रह संचार
Explanation
Samuel Morse developed Morse code, which is used in the telegraph to send messages using signals made of dots and dashes.
Question 2
In whose name was the telephone patent registered in 1876?
- Aगुग्लिएल्मो मार्कोनी
- Bसैम्युअल मोर्स
- Cजॉन लॉगी बेयर्ड
- Dअलेक्ज़ेंडर ग्राहम बेल
Explanation
Alexander Graham Bell patented the telephone in 1876, which converts sound into an electrical signal and sends it.
Question 3
Radio waves can travel through a vacuum, but sound waves cannot — what is the reason for this?
- Aरेडियो तरंगें विद्युत-चुम्बकीय हैं, ध्वनि तरंगों को यात्रा के लिए माध्यम चाहिए
- Bरेडियो तरंगें बहुत धीमी होती हैं
- Cध्वनि तरंगें प्रकाश से तेज़ होती हैं
- Dइनमें कोई अंतर नहीं है
Explanation
Radio waves are electromagnetic, so they don't need a medium to travel, while sound waves need a medium such as air to vibrate through.
Question 4
Indian scientist Jagdish Chandra Bose is known for which achievement?
- Aटेलीफोन का आविष्कार
- Bसन् 1895 में कोलकाता में बिना तार संकेत भेजने का प्रदर्शन
- Cटेलीविज़न का आविष्कार
- Dउपग्रह प्रक्षेपण
Explanation
Indian scientist Jagadish Chandra Bose publicly demonstrated sending a wireless signal in Kolkata in 1895, which is considered to have come before Marconi's famous demonstrations.
Question 5
In what form does a signal travel in an optical fibre cable?
- Aध्वनि तरंग के रूप में
- Bचुम्बकीय क्षेत्र के रूप में
- Cप्रकाश (लेज़र) के रूप में
- Dऊष्मा के रूप में
Explanation
Optical fibre is a thin glass/plastic wire in which the signal travels as light rather than electricity, which allows data to be sent quickly.
Question 6
In a mobile (cellular) network, a city is divided into small parts — what are these called?
- Aज़ोन
- Bनोड
- Cग्रिड
- Dसेल
Explanation
In a mobile network, an area is divided into small 'cells', each with a tower that connects to phones via radio waves — this is why it is called a cellular network.
Question 7
Which organization operates the INSAT/GSAT series of satellites for satellite communication in India?
- AISRO
- BBSNL
- CDRDO
- DAIIMS
Explanation
India's Indian Space Research Organisation (ISRO) operates the INSAT/GSAT series of satellites for tasks such as telecommunication, broadcasting and weather monitoring.
Question 8
Through the 'tin-can telephone' activity (two tin cans and a string), what does the teacher mainly want to explain to students?
- Aरेडियो तरंगों का सिद्धांत
- Bध्वनि कंपन के यांत्रिक संचरण का विचार
- Cउपग्रह संचार का सिद्धांत
- Dऑप्टिकल फाइबर का सिद्धांत
Explanation
The tin-can telephone activity shows how sound vibrations can travel along a string — it is an activity that simply explains sound transmission and the basic idea behind the telephone.
Question 9
Arrange the telegraph, telephone, radio and television in the correct chronological order of their invention (earliest to latest).
- Aटेलीफोन → टेलीग्राफ → टीवी → रेडियो
- Bरेडियो → टेलीग्राफ → टेलीफोन → टीवी
- Cटेलीग्राफ → टेलीफोन → रेडियो → टीवी
- Dटीवी → रेडियो → टेलीफोन → टेलीग्राफ
Explanation
The correct chronological order is: telegraph (1844) → telephone (1876) → radio (1895/1901) → television (1925-26).
Question 10
Which teaching aid would be most suitable for helping students remember the history of telecommunication in class?
- Aकेवल पाठ्यपुस्तक पढ़ना
- Bकोई सहायक सामग्री न देना
- Cकेवल परिभाषाएँ रटवाना
- Dआविष्कारों की समयरेखा (timeline chart)
Explanation
A timeline chart helps children see and remember the order in which these technologies developed, in a visual form, which is more effective than just reading or memorising.
Frequently asked questions
Who invented the telegraph?+
Samuel Morse developed Morse code and sent the first public telegraph message in 1844.
Who holds the patent for the telephone?+
The telephone was patented by Alexander Graham Bell in 1876.
What is the difference between radio and sound waves?+
Radio is based on electromagnetic waves, which can travel even through a vacuum; sound waves need a medium such as air to travel — which is why sound cannot be heard in space (a vacuum), but radio signals can be sent.
Does Jagadish Chandra Bose have any connection to radio?+
Yes — Indian scientist Jagadish Chandra Bose publicly demonstrated sending a signal without wires in Kolkata in 1895, which is considered to have come before Marconi's famous public demonstrations, although the commercial development of radio is credited to Marconi.
How many questions come from telecommunication in REET?+
This topic is part of the 'Science in Daily Life' section of the REET Level 2 Science syllabus, but no verified direct question came from it in REET 2024 — since it is in the syllabus, a question may appear in the future.
Why is optical fibre considered better than a copper wire?+
In optical fibre, the signal travels as light, which lets data be sent very fast, over long distances, with very little signal loss — this is why today's internet backbone relies mainly on optical fibre.
Read next
Official Sources
Change Log
- 17 September 2026 — English page published — mirrors the fact-checked Hindi page, independently bilingual-accuracy checked