PURPOSE:To prevent information from being leaked to other groups to which the specific information should not be transmitted by allowing the 1st station to supervise automatically a number specific to a mobile station. CONSTITUTION:The 1st station A transmits a radio wave only to an area 3 so as to deliver a call signal. A mobile station 5 receiving the call signal transmits a number specific to the own station to the 1st station A when the call signal is a certain level or over. The 1st staion A confirms whether the specific number received from a mobile station 5 is a group being an object of transmission of specific information or not and transmits the specific information into the area 3 only when it is confirmed. The mobile station 5 receiving the specific information adds a signal of reception confirmation to the specific number of the own station and transmits a signal to the 1st station A. When the 1st station A receives the specific number and the signal of reception confirmation from the mobile station 5, the station A completes the transmission of information to the mobile station 5. The specific number of the own station is read from a memory and the specific number and the signal of reception confirmation are transmitted from the transmitter through an antenna via a switch.
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