This circuit for audio applications was found in an English magazine from the 80's. The circuit has a pass band below 3 kHz making it ideal for telecom applications.
This circuit turns on and off when a short pulse is applied by SW to the input of the first...
This circuit was found in a 1970 US publication. Transistors are still common and the circuit can be...
This circuit locks after a short touch on the sensor. The circuit can be powered by voltages from 5...