We found this circuit in the July 1994 Radio Electronics magazine. The circuit uses a general-purpose transistor, and the power supply can be up to 12 V depending on the relay.
This highly sensitive light sensor was found in a 1970 General Electric documentation. The circuit...
The given number circuit is used to activate the relay by interrupting the light beam that hits...
This alarm circuit with sensors in series was found in the Electronics Now magazine of June 1994....