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 2 meter (144 MHz) preamplifier is intended for use with portable transceivers. The...
This circuit from a Popular Electronics from the 90s uses a common optocoupler and a...
The existence of field effect transistors at the input of the integrated circuit (operational...