This old voice circuit suitable for telephones of the time was found in a Radio Electronics from September 1973. The circuit is powered by a voltage of 7 V.
In the figure we have a transmitter and a simple remote-control receiver for tests found in a 90s...
The configurations of the two previous circuits can be modified to operate with a simple power...
This circuit uses a symmetrical power supply, and the motor is for the voltage indicated in the...