Subscriber alarm system

Claim 1

AN ALARM SYSTEM COMPRISING A PAIR OF CONDUCTORS CONNECTING A REMOTE CIRCUIT TO A CENTRAL ALARM CIRCUIT, MEANS AT THE REMOTE CIRCUIT FOR COMPLETING A CIRCUIT BETWEEN SAID PAIR OF CONDUCTORS ON THE OCCURRENCE OF AN EVENT, ALARM MEANS AND A UNIDIRECTIONAL CURRENT ELEMENT CONNECTED IN SERIES CIRCUIT ACROSS SAID PAIR OF CONDUCTORS AT THE REMOTE CIRCUIT, SAID CENTRAL ALARM CIRCUIT INCLUDING A SOURCE OF POTENTIAL, SWITCH MEANS HAVING AT LEAST TWO POSITIONS, SECOND ALARM MEANS CONNECTED IN CIRCUIT WITH SAID SOURCE OF POTENTIAL AND SAID SWITCH MEANS, SAID SWITCH MEANS CONNECTED TO SAID PAIR OF CONDUCTORS AND ADAPTED IN ONE POSITION TO CONNECT SAID CONDUCTORS IN CIRCUIT WITH SAID SOURCE OF POTENTIAL AND SECOND ALARM WHEREBY SAID SECOND ALARM IS ENERGIZED BY SAID MEANS AT THE REMOTE CIRCUIT UPON THE OCCURRENCE OF AN EVENT, AND SAID SWITCH MEANS ADAPTED IN THE OTHER POSITION TO CONNECT SAID CONDUCTORS IN CIRCUIT WITH SAID SOURCE OF POTENTIAL TO CAUSE CURRENT FLOW THROUGH SAID UNIDIRECTIONAL CURRENT ELEMENT AND ENERGIZE SAID ALARM MEANS AT THE REMOTE CIRCUIT WHEREBY REVERSE SIGNALING IS OBTAINED IN SAID PAIR OF CONDUCTORS.