Patent ID: 7489231

Claim:
An electromagnetic wave reception device used with a transmission device having a predetermined transmission duration, comprising: an input reception portion for detecting an input electromagnetic wave transmitted from a transmission terminal at a predetermined timing and receiving the input electromagnetic wave; a lock control portion for unlocking or locking a lock mechanism according to the input electromagnetic wave received by the input reception portion; and a timing change portion for changing a duration of intervals between detection periods, the detection periods being periods at which the input reception portion detects the input electromagnetic wave, wherein the timing change portion changes the duration of the intervals between the detection periods to be shorter when input electromagnetic waves are detected a plurality of times for a predetermined period of time such that the duration of the intervals between the detection periods of the reception device, prior to the change of the duration, is longer than the predetermined transmission duration of the transmission device and the duration of the intervals between the detection periods of the reception device, subsequent to the change of the duration, is shorter than the predetermined transmission duration of the transmission device.