Polarized d.c. signaling system and means for supervising same

Claim 1

IN A SIGNALING SYSTEM, A SIGNALING LINE COMPRISING TWO CONDUCTORS, A SOURCE OF D.C. POTENTIAL NORMALLY CONNECTED TO SAID LINE TO MAINTAIN ONE CONDUCTOR THEREOF POSITIVE AND THE OTHER CONDUCTOR NEGATIVE, A PLURALITY OF CIRCUITS BRIDGING SAID LINE AT INTERVALS ALONG ITS LENGTH, EACH OF SAID BRIDGING CIRCUITS COMPRISING, IN SERIES, A PAIR OF DIODES WITH A SIGNAL RESPONDING DEVICE INTERMEDIATE THE DIODES, SAID DIODES BEING SO POLED AS TO NORAMALLY PREVENT THE FLOW OF CURRENT FROM SAID SOURCE THOUGH SAID DEVICES, MEANS FOR AT TIMES REVERSING THE POLAIRTY OF THE D.C. POTENTIAL CONNECTED TO SAID LINE THEREBY TO OPERATE SAID DEVICES, A SUPERVISORY CIRCUIT NORMALLY ENERGIZED BY DIRECT CURRENT FROM SAID SOURCE AND HAVING MENAS FOR RESPONDING TO A CESSATION OF THE CURRENT FLOW IN SAID SUPERVISORY CIRCUIT, SAID SUPERVISORY CIRCUIT INCLUDING BOTH CONDUCTORS OF SAID LINE IN SERIES, MEANS CONNECTING SAID SOURCE AND ALL OF SAID DEVICES IN SERIES INDEPENDENTLY OF SAID LINE TO FORM A SECOND NORMALLY ENERGIZED SUPERVISORY CIRCUIT, AND MEANS CONTROLLED BY SAID SECOND SUPERVISORY CIRCUIT TO OPERATE RESPONSIVE TO A CESSATION OF THE CURRENT FLOW IN SAID SECOND SUPERVISORY CIRCUIT.