We found this circuit in the July 1992 issue of Radio Electronics magazine. An optical system produces the light beam that, when interrupted, triggers the alarm. The sensitivity is adjusted by R4.
This simple timer, which activates an LED indicator, but which can be modified to activate a...
This circuit was obtained in a documentation for radio amateurs in 1974. The coil consists of 12...
This circuit was found in a 1973’s Japanese magazine. It uses transistors of the time and is...