Inventors:
Angelo P. DeBenedictis - Carlisle MA
Plato Zorzy - Salem MA
International Classification:
G08B 310
Abstract:
A system for producing an alarm whenever the distance between a transmitter and a receiver exceeds a predetermined distance. The transmitter includes circuitry for generating a signal having a preselected pulse code modulation pattern. The receiver includes circuitry for responding to the particular pulse code pattern and for sounding an alarm when the signal from the transmitter is so weak that pattern is not received.