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 is another practical idea found in a 1997 documentation. This circuit allows a DJ to change the...
This circuit uses two 4001 ports to drive a relay. The circuit is from Electronics Now magazine, July...
This circuit is based on an LM3900 transconductance operational amplifier, found in 1992...