We found this circuit in an Electronics Now from the 1990s. The circuit crashes when light strikes the sensor. Instead of the alarm a relay can be used to drive higher power devices.
This circuit was found in a Mullard transistor manual from 1960. Note the symmetrical power...
With the shadow over the sensor, it is possible to interrupt the sound of your amplifier using this...
This circuit puts the battery in the circuit when the voltage of a source is cut, preventing it...