We found this circuit in the September 1971 Radio Electronics magazine. The SCR can be any of the 106 series and the buzzer can be replaced by a relay according to the supply voltage.
This circuit is a handset receiver that picks up the signal emitted by a coil under the rug or...
This circuit uses a capacitor to store energy. The capacitor is charged by closing S1 by a moment. Them,...
This circuit filters low frequency noise from the turntable motor. We found it in a 1989...