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 beat frequency oscillator or BFO was found in an American 1980s documentation. The circuit is...
This circuit is from the 1990 Motorola Linear Databook. The circuit can be implemented with other...
In the figure we have the simple way of controlling a load or having a signal from an optical...