Telephone Communications

How do telephones convert your voice so that it travels over phone lines?
Answered by Science Channel
  • Science Channel

    Science Channel

  1. First, a microphone in the telephone converts the sound waves into electricity. Sound waves are waves of varying pressure -- the sound physically pushes against a diaphragm in the microphone. Some old telephones use a diaphragm pressed against tiny granules of carbon. As the diaphragm compresses the granules, their electrical resistance changes. Running a current through the granules allows the telephone to send varying electrical waves through a telephone line. The phone on the other end converts these electrical waves back into physical sound waves using a small speaker in the receiver. Other phones may use electromagnets to induce electricity in copper wire. It still works in basically the same way -- movements from the diaphragm create varying waves of electricity.

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