Class as unit except for experiments
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
- 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
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.
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.
/ 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.
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.
- Making a String Telephone (group work)
- Sound travelling through a string - making a string telephone.
is used to record experiments.