Remote control system, particularly to lock/unlock car doors

A non-contact data carrier includes a battery (29), an electric-supply circuit (4) for rectifying a received carrier signal and generating power, and an electric-supply switching circuit (9) for comparing the voltage of the battery and the voltage generated by the electric-supply circuit and selecting either one of the voltages. When the battery (29) can supply power, long-distance communication can be performed by supplying power from the battery. In case of battery exhaustion, power is supplied from the electric-supply circuit (4) which receives a stronger carrier signal by using the non-contact IC card in the proximity of a question unit and rectifies the carrier signal, so that the function of the non-contact data carrier is maintained.