To make switching operation easier by changing an objective device with a remote controller, adding a rolling synchronization circuit thereto, and thereby avoiding lost motion at operating a plurality of security devices respec tively by means of a common remote controller.

A security device 2 equipped with an antenna 30 for receiving signals from a remote controller unit, an ignition switch 44, a door switch 46, etc., is installed on each vehicle, and the security device 2 is operated by a common remote control unit. Besides, the security device 2 includes an impact sensor 48, a radar 50 and the like, and is formed to malfunction even when the window is broken and someone comes therein. In situations where a vehicle to be an objective in the control of security operation is changed, frame synchronization data, an ID code, a function code, a rolling code, and a rolling synchronization code are transmitted from the remote control unit. Receiving these signals with the antenna 30 allows to operate the security device 2. In this way, switching operation can be done simply.