Vehicle detector with capacitor storage element

Claim 1

A VEHICLE DETECTOR COMPRISING: AN ELECTRONIC AMPLIFYING DEVICE HAVING FIRST AND SECOND CONTROL TERMINALS AND AN OUTPUT TERMINAL, FOR SUPPLYING AN OUTPUT SIGNAL IN RESPONSE TO THE RELATIVE POTENTIAL BETWEEN SAID FIRST AND SECOND CONTROL TERMINALS; A DETECTOR LOOP; CIRCUITRY CONNECTED TO SAID LOOP AND SAID FIRST INPUT TERMINAL FOR VARYING THE POTENTIAL OF SIAD FIRST TERMINAL IN RESPONSE TO A CHANGE IN THE IMPEDANCE OF SAID LOOP; A CIRCUIT CONNECTED TO RECEIVE SAID OUTPUT SIGNAL AND CONNECTABLE TO OPERATE A RECORDING DEVICE IN ACCORD WITH A CHANGE IN ONE SENSE, OF SAID OUTPUT SIGNAL; A FEEDBACK TERMINAL CONNECTD TO SAID LAST MENTIONED CIRCUIT SAID CIRCUIT FOR PRODUCING AT THE FEEDBACK TERMINAL, A FEEDBACK SIGNAL OF A VALUE WHICH, IF APPLIED TO A SECOND CONTROL TERMINAL OF SAID ELECTRONIC AMPLIFYING DEVICE, WOULD COMPENSATE FOR THE CHANGE AT THE FIRST INPUT TERMINAL SUFFICIENTLY TO PREVENT SUBSTANTIVE VARIATION OF SAID OUTPUT SIGNAL;