How Telephones Work: VIDEO/DVD, We speak into the telephone; we hear the voice of the caller, but how do the voices travel from one telephone to the other? Bob Symes opens up a telephone receiver to find the answer. A microphone made of loosely packed carbon granules changes the electricity that passes through; the electricity moves a metal plate (the diaphragm); the density of the carbon granules depends on the pressure of the sound reaching them.


			How Telephones Work

We speak into the telephone; we hear the voice of the caller, but how do the voices travel from one telephone to the other? Bob Symes opens up a telephone receiver to find the answer. A microphone made of loosely packed carbon granules changes the electricity that passes through; the electricity moves a metal plate (the diaphragm); the density of the carbon granules depends on the pressure of the sound reaching them. (7 minutes)

ORDER CODE: FFMBVL1654V
VHS VIDEO

ORDER CODE: FFMBVL1654DVD
DVD