This 4-transistor timer was found in the April 1975 issue of Radio Electronics magazine. It uses both single-ended and single-junction transistors to provide a dual audio output.
Found in a General Electric documentation from the 1980s, this circuit makes use of a FET...
This circuit is based on an MC1408, an integrated circuit that is not common today. The...
Another way to increase the sensitivity of the circuit with the amplification of the sensor...