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 English documentation from the 1980s, this circuit can use any germanium diode. The...
This configuration, which requires a symmetrical power supply for the 741, can be implemented with other...
This 3-digit code switch was obtained from an old American documentation. The capacitor is 470 uF...