Automatic control system for vehicles incorporating a ranging system for vehicle traffic safety control

Claim 1

IN A SYSTEM FOR AUTOMATICALLY CONTROLLING THE OPERATION OF VEHICLES IN ACCORDANCE WITH LOCAL ROUTE CONDITIONS, THE COMBINATION COMPRISING: (A) RECEIVER MEANS RESPONSIVE TO SIGNALS FROM WAYSIDE REPRESENTING MAXIMUM SPEED LIMITS FOR SELECTIVELY ENERGIZING DEVICES ESTABLISHING CORRESPONDING SPEED ASPECT INDICATIONS ON BOARD SAID VEHICLE; (B) MEANS ON BOARD SAID VEHICLE FOR DERIVING A RANGE SIGNAL WHICH INCREASES IN VALUE AS A FUNCTION OF INCREASING DISTANCE BETWEEN SAID VEHICLE AND AN OBSTRUCTION IN ADVANCE THEREOF; (C) MEANS RESPONSIVE TO SAID RANGE SIGNAL FOR SELECTIVELY ENERGIZING DEVICES ESTABLISHING A NUMBER OF DISCRETE RANGE ASPECT INDICATIONS; (D) A PLURALITY OF REFERENCE SIGNAL SOURCES; (E) SELECTOR MEANS OPERATIVE TO PROVIDE FOR THE SELECTION OF A REFERENCE SIGNAL SOURCE IN ACCORDANCE WITH THE LOWEST ORDER ASPECT INDICATION ESTABLISHED; AND (F) MEANS FOR COMPARING THE REFERENCE SIGNAL SO SELECTED WITH A SIGNAL PROPORTIONAL TO THE ACTUAL SPEED OF SAID VEHICLE TO PROVIDE AN ERROR SIGNAL.