To reduce the cost of the whole of a device by having a relatively simple composition and extending the range of a starting signal toward the outside of an automobile.

In the case of the transmission of the starting signal from a receiver 3 to an electronic key 2, an unmodulated starting signal is transmitted toward the outside of the automobile, and a modulated starting signal is transmitted toward the inside of thereof. When the electronic key 2 is outside the automobile, the discrimination of the starting signal is made unnecessary and a control part 26 has only to be able to be started by the received signal. Consequently, the starting signal toward the outside of the automobile is made unmodulated so as to be able to extend the substantial range.