We found this circuit that triggers an SCR in the Encyclopedia of Electronic Circuits volume 5 of 1995. The circuit is powered by voltage according to the warning load.
This circuit was obtained from the Radio Electronics magazine of October 1960. The circuit uses a...
Found in an Electronics World of 1966, this circuit makes use of FETs of the time. Modern...
Found in a 90s 303 Circuits, this circuit triggers a load from a 50 mV audio signal. When the...