Inductive loop vehicle detector

• US 3,346,856 A
• Filed: 07/06/1964
• Issued: 10/10/1967
• Est. Priority Date: 07/06/1964
• Status: Expired due to Term

• Current Assignee: Lawrence Sepe, Robert J. Miller, Robert N. Doble
• Original Assignee: Lawrence Sepe, Robert J. Miller, Robert N. Doble
• Inventors: Doble, Robert N., Miller, Robert J., Sepe, Lawrence
• Application Number:
  US04/380,559
• Time in Patent Office: 1,191 Days
• US Class Current: 340/939
• CPC Class Codes: B61L 13/047 controlling inductively or magnetically
• CPC Class Codes: G08G 1/042 using inductive or magnetic detectors

Claims

1. A VEHICLE DETECTION SYSTEM COMPRISING A FIRST OSCILLATOR INCLUDING AN INDUCTIVE LOOP, A SECOND OSCILLATOR, A MIXER CIRCUIT COUPLED TO BOTH OSCILLATORS FOR GENERATING DIFFERENCE FREQUENCY SIGNAL, A DISCRIMINATOR COUPLED TO THE MIXER CIRCUIT FOR GENERATING A DIRECT SIGNAL LEVEL CORRESPONDING TO THE DIFFERENCE FREQUENCY, MEANS FOR AMPLIFYING THE DIRECT SIGNAL LEVEL, AN AUTOMATIC FREQUENCY CONTROL CIRCUIT COUPLED TO CONTROL THE FREQUENCY OF THE SECOND OSCILLATOR FROM THE DIRECT SIGNAL LEVEL, A MEANS FOR STORING A SIGNAL LEVEL CORRESPONDING TO THE DIRECT SIGNAL LEVEL, A SIGNAL STORING MEANS HAVING DUAL TIME CONSTANT SPATHS WHEREBY A SIGNAL LEVEL MAY BE RECEIVED RELATIVELY- FAST AND MAY BE DISSIPATED RELATIVELY SLOWLY, AND A SWITCHING MEANS COUPLED TO THE DIRECT SIGNAL LEVEL AND TO THE SIGNAL LEVEL STORING MEANS, AND SWITCHING MEANS BEING RESPONSIVE TO THE RELATIVE VALUES OF THE DIRECT SIGNAL LEVEL AND THE STORED SIGNAL LEVEL.