This three-transistor circuit was found in Radio Electronics magazine from May 1969. The circuit is for hearing aids and has earphone listening.
This audio generator that produces both rectangular and sinusoidal signals was found in a...
This simple circuit for a high impedance magnetic phone (500 ohms or more) has been found in a...
Found in an American publication from 1968, this circuit can be made based on a TIP42 that must be...