This circuit was obtained from an American 1980s documentation. The frequency depends on the crystal and the circuit may be a PNP that reaches the generated frequency.
This 16-second voice recording circuit was featured in a telephone answering machine circuit in...
The intensity of an audio signal can be controlled by a remote potentiometer on a DC circuit,...
This circuit was obtained from an old Signalite documentation. Neon lamps are special types of the...