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.
This circuit was found in a 1990 Electronics Handbook. The transistors can also be the BC548 and...
This circuit is from a 1987 American publication called Electronics Handbook. The circuit can be...
This 1995 documentation circuit detects when an extension on a phone line is active. Adjustment of the...