This circuit triggers a buzzer or other warning device when the light falling on the sensor is cut off. We found it in the Encyclopedia of Electronic Circuits Volume 5 of 1995.
We found this circuit in a 1967 Electronic Design. The circuit used a MOSFET of the time, which is...
This circuit was found in a 1967 RCA SCR manual. It uses period components that can be replaced with...
We found this circuit in the October 1992 issue of Radio Electronics magazine. The duty cycle can...