This alarm circuit triggers when S1 opens. The circuit from a January 1975 Radio Electronics magazine can be used with interrupt sensors connected in series.
This immobilizer circuit for the car was found in the Radio Electronics magazine of December 1976....
This circuit allows the activation of a remote telephone bell made with a common piezoelectric capsule. The...
This circuit can act as a receiver for the transmitter of the previous circuit. We found it in...