This circuit was found in an English publication from 1967. The circuit is for listening on a phone. Transistors are types of germanium of the time.
This is a field strength meter found in an 80's Hands On. The circuit operates at frequencies up to 500...
Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the...
This circuit can generate signals from 100 kHz to 50 MHz depending on the crystal and the...