Radio communication devices receive timing reference pulses from a timing generation device and can acquire synchronism based on the received pulses, so that even on the ultra wide band (UWB) radio communication system, where there is no carrier as exists in the conventional radio communication systems, there is no need to add a redundant preamble signal ahead of transmitted information in order to acquire initial synchronism. In order to receive an asynchronous signal, there is no need to perform detection for a very long time to find whether the signal is present or absent. The application of an access control system according to the present invention to UWB radio communication implements high-speed asynchronous radio communication.