Patent ID: 7109887

Claim:
In a vehicle detector having circuitry powered by a source of electrical power for sensing changes in an associated inductive loop related to the presence of a vehicle in the vicinity of the loop and for generating a Call signal in response to such changes; the improvement comprising means for automatically performing a loop check for the associated inductive loop, said means for automatically performing a loop check including a separate check loop located adjacent said inductive loop and switch means for selectively coupling said check loop to said vehicle detector, said vehicle detector including means for periodically activating said switch means to couple said check loop to said vehicle detector, means for activating said check loop to simulate a vehicle load on said inductive loop when said check loop is coupled to said vehicle detector, and means for determining the inductance value of said inductive loop when said check loop is activated, said means for automatically performing a loop check including additional testing circuitry for performing an iterative loop integrity test on an inductive loop, said additional circuitry including means for determining an initial loop check failure, means for establishing a maximum number of iterative loop checks, timer means for establishing the time between successive iterative loop checks, means for enabling said iterative loop integrity test after said initial loop check failure, fail means for determining whether said inductive loop fails a given iterative loop check, and iterative loop check stop means for terminating said iterative loop integrity test when said fail means determines that said inductive loop failed said maximum number of successive loop checks.