Strand:Energy and Forces

Lesson: The Telephone


That the children will be able to:
1. Give brief history of the telephone
2. Name parts of the telephone
3. Understand how voices transmitted through a telephone network
4. Understand the importance of optical fibre to carry telephone calls
5. Name other electronic devices which communicate using telephone links
6. Appreciate the role of telephone exchanges in local and long-distance / international calls.

Materials Needed

Textbooks: Look Around 6th Class (Folens)
Young Scientist Vol 16
Laptop and Projector; Digital Camera and Extension Lead
CD Rom - "The Way Things Work"
String, Plastic Cups, Pencil, Scissors, Pin



Organisation: Class as unit except for experiments

1. Introduce A.G. Bell 1876, America

2. How telephone works: Voices make vibrations called sound waves. Each sound wave can be turned into an electronic signal which can travel along a wire.


3. Caller - Telephone exchange - Receiver via trunk line (telephone motorway). Phoning another country, signal travels via undersea cable or land line or via satellite in space or may pass directly between the exchanges.

4. Microphone in the mouthpiece changes sound of voice into an electronic signal. In friend's telephone, a small loudspeaker in the earpiece changes the signal back into the sound of your voice.

5. Optical Fibre - A thin strand of flexible glass or plastic, the width of a human hair. They are bunched together like electric wires to make a cable which can carry 1,000'2 of messages. When light is shone into one end, it travels along the fibre to the end. The Electric signal from a telephone can be changed into light signals and sent along the optical fibre.

6. Computers / Fax Machines - how they use telephone lines



CD Rom - "The Way Things Work"
Click on 'Inventors', then click on 'Bell'. Here children can learn an interesting story about the invention of the telephone.

Clicking on 'Telephone' shows them the parts, how to make a local / long-distance call. The telephone is shown being dialled and the routing via exchanges. Children can listen to a phone call to Chicago where an answering machine was reached.


Experiment - Making a String Telephone (group work)

Discuss experiment - Sound travelling through a string - making a string telephone.

Digital camera is used to record experiments.

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