Highway crossing protection system

Claim 1

IN A HIGHWAY CROSSING PROTECTION ARRANGEMENT FOR A STRETCH OF MULTIPLE TRACK RAILROAD HAVING A PLURALITY OF HIGHWAY CROSSINGS, EACH SUCH CROSSING BEING PROVIDED WITH A WARNING DEVICE FOR HIGHWAY TRAFFIC, THE COMBINATION COMPRISING, (A) A PLURALITY OF SETS OF PARALLEL OVERLAY TRACK CIRCUITS, EACH SET SERVING FROM A SINGLE TRANSMITTER HAVING A FREQUENCY DIFFERENT FROM EACH OTHER TRANSMITTER FOR DETECTING THE PRESENCE OF A TRAIN IN PREDETERMINED PARALLEL LENGTHS OF SAID MULTIPLE TRACKS, (1) SAID PREDETERMINED LENGTHS BEING SO POSITIONED THROUGHOUT SAID STRETCH AS TO PROVIDE CONTINUOUS DETECTION OF A TRAIN MOVING ON ANY OF SAID MULTIPLE TRACKS, (B) A SET OF CODING CONTACTS FOR EACH SAID OVERLAY CIRCUIT SET CONTINUOUSLY OPERABLE IN SUCCESSION BE TWEEN A SERIES OF CONTACT POINTS AND CONNECTED FOR APPLYING THE CORRESPONDING TRANSMITTER SIGNAL SUCCESSIVELY TO EACH OF SAID MULTIPLE TRACKS TO ELIMINATE MUTUAL INTERFERENCE BETWEEN THE PARALLEL LENGTHS OF TRACK, (C) AN ACTUATING CIRCUIT ARRANGEMENT FOR EACH SAID WARNING DEVICE CONTROLLED BY SAID OVERLAY TRACK CIRCUIT SET FOR OPERATING THE ASSOCIATED WARNING DEVICE ONLY UPON THE APPROACH OF TRAIN WITHIN A PRESELECTED DISTANCE OF THE CORRESPONDING CROSSING FROM EITHER DIRECTION ON ANY OF SAID MULTIPLE TRACKS.