Patent ID: 6535143
Filing Date: 2003-03-18
Classification: G07B,G08G

Abstract:
A vehicle detection system for detecting an arrival of a predetermined vehicle provided with a transponder and a vehicle without the transponder comprising;a first inductive element of a loop coil disposed at a parking car road for functioning as transmitting and receiving means, a first vehicle detection circuit connected to the inductive element, wherein said transponder mounted on the predetermined vehicle stores information which identifies the predetermined vehicle, periodically activated by the magnetic field which first inductive element generates, periodically transmits the stored information to the vehicle detecting circuit via the first inductive element, characterized in that the vehicle detecting circuit intermittently stimulated the inductive element to generate the magnetic field, the vehicle detecting circuit receives the stored information from the transponder during a non-stimulating period for the first inductive element to identify the predetermined vehicle when the transponder mounted vehicle has entered into a specified area around the first inductive element, and the vehicle detecting circuit detects the arrival of a vehicle by detecting a phase change between the magnetic field during non-existence of the vehicle around the first inductive element and the magnetic field during an existence of the vehicle around the first inductive element, the phase change being caused by a change of inductance in the first inductive element.