00:01
Here we're going to quickly look at the electrical design known as a carbon microphone.
00:09
These were used in telephones for many years in the speaker end.
00:15
And maybe if you take part an older telephone, you will actually find this.
00:21
But the way they worked is you have a sound wave that would hit a loose diaphragm that could move in response to the way.
00:31
That diaphragm was connected to a battery with a back end also in the circuit.
00:40
And that would be loosely packed carbon granules between the two faces of the microphone, sandwiched in there.
00:51
And as the sound wave made the diaphragm move back and forth, the carbon granules would become compact and then rarefied, compact, etc.
01:01
Now, carbon is not a metal, but it does conduct electricity, and even to this day is made into resistors.
01:12
So the circuit would basically look like a voltage hooked to a variable resistance...