On Jun 30, 12:55 pm, John Smith I wrote:

Use simple logic, you can modulate a dc (0 Hz) with higher freq (voice),
(hint, your telephone line is an example) right?

The telephone does not use either AM or FM. It is simply the
electrical equivalent of the sound that gets into the microphone. You
input a 1 KHz tone into the microphone, telephone lines will carry a 1
KHz AC current to the destination. The louder the sound into the
microphone, the stronger the amperage in the telephone lines.