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 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...