Passive guidance system

Claim 1

IN A SYSTEM FOR AUTOMATICALLY GUIDING VEHICLES HAVING STEERING MEANS ALONG A BIDIRECTIONAL ROADWAY, THE SYSTEM COMPRISING A CLOSES LOOP FOR CONDUCTIVE MATERIAL DISPOSED IN THE RAODWAY SUCH THAT A FIRST PORTION OF THE LOOP DEFINES A DESIRED PATH OF VEHICLES TRAVEL IN ONE DIRECTION ALONG THE ROADWAY AND A SECOND PORTION OF THE LOOP DEFINES A DESIRED PATH OF VEHICLE TRAVEL IN THE OPPOSITE DIRECTION ALONG THE ROADWAY, A SIGNAL TRANSMITTER MOUNTED ON THE REAR OF EACH VEHICLE, THE TRANSMITTERS MOUNTED ON THE VEHICLES PROCEEDING IN ONE DIRECTION OPERATING AT A FIRST PREDETERMINED FREQUENCY AND THE TRANSMITTERS MOUNTED ON VEHICLES PROCEEDING IN THE OPPOSITE DIRECTION OPERATING AT A SECOND PREDETERMINED FREQUENCY, THE TRANSMITTERS BEING COUPLED TO THE LOOP TO INDUCE RESPECTIVE SIGNALS THEREIN AT THE FIRST AND SECOND PREDETERMINED FREQUENCIES, WHEREBY THE LOOP RADIATES AN ELECTROMAGNETIC FIELD ABOVE THE ROADWAY, THE ELECTROMAGNETIC FIELD HAVING COMPONENTS AT THE FIRST AND SECOND PREDETERMINED FREQUENCIES, A PICKUP MOUNTED ON THE FRONT OF EACH VEHICLE AND RESPONSIVE TO THE ELETROMAGNETIC FIELD TO PRODUCE A GUIDANCE SIGNAL INDICATIVE OF THE DEVIATION OF THE VEHICLE FROM THE DESIRED PATH, FREQUENCY SELECTIVE MEANS CONNECTED TO THE PICKUP TO PASS ONLY THOSE SIGNALS SUBSTANTIALLY CORRESPONDING TO THE FREQUENCY OF THE TRANSMITTER MOUNTED ON THE VEHICLE, SERVO MEANS CONNECTED TO THE FREQUENCY SELECTIVE MEANS AND TO THE VEHICLE STEERING MEANS AND RESPONSIVE TO THE GUIDANCE SIGNAL TO MAINTAIN THE VEHICLE IN THE DESIRED PATH.