Patent ID: 7353185

Claim:
An electronic toll collection system for a toll road which collects a toll from a vehicle passing a quasi communication area and reaching a standard communication area, comprising: a road-side device; first means, provided in the road-side device, for transmitting a polling signal, the polling signal at the quasi communication area having an electric field strength between a first electric field strength and a second electric field strength larger than the first electric field strength, the polling signal at the standard communication area having an electric field strength equal to or higher than the second electric field strength, an on-vehicle device of the vehicle positioned in the standard communication area being able to respond to the polling signal many times and to communicate with the road-side device; second means, provided in the road-side device, for receiving a plurality of responses of a single on-vehicle device to the polling signal transmitted by the first means without receiving another signal in the on-vehicle device, the on-vehicle device being positioned in the standard communication area during the responses; third means, provided in the road-side device for deciding whether or not the second means receives a response a plural number of times; and fourth means, provided in the road-side device, for deciding that the on-vehicle device is now positioned in the standard communication area when the third means decides that the second means receives the plurality of responses to the polling signal and starting a communication with the on-vehicle device positioned in the standard communication area.