Abstract: A remote-control-operated locking/unlocking system includes a key which transmits a locking/unlocking signal by remote control. A locking/unlocking unit is provided with a controller for controlling a locking/unlocking operation based on a locking/unlocking signal transmitted from the key. The controller has a suitability determining section for determining the suitability of a locking/unlocking signal transmitted from the key, and an information section for providing information indicating that the use of the key is unsuitable.

Abstract: A transmission and reception system for controlling a locking/unlocking operation of a key includes a transmission section for transmitting a control signal having a predetermined frequency for effecting locking/unlocking of the key, and a reception section for receiving the control signal and effecting driving control of the key in response to the control signal. The reception section includes a carrier detection circuit for detecting a frequency of the control signal and supplies power only to the carrier detection circuit when the control signal is not received.