Using an LDR as a sensor and an operational amplifier this circuit was found in the Encyclopedia of Electronic Circuits volume 5 from 1995. The circuit triggers an optodiac.
This circuit is from a March 1978 Radio Electronics magazine article that showed how to build it....
This circuit was obtained from an article in Radio Electronics magazine in October 1966. It...
In the figure we have a bistable circuit that activates LEDs from touch rings and turns off data...