| 摘要 |
In a mobile communication system comprising a plurality of base stations disposed in respective radio zones, a portable telephone set (20) comprises a radio transmission/reception section (24) for receiving a first area identification signal transmitted from a first base station. A main RAM (22) holds the first area identification signal as a current area identification signal. Responsive to an incoming call signal for the first base station, a main CPU (21) determines whether or not a user of the portable telephone set answers to the incoming call signal within a predetermined time interval elapsed since the incoming call signal is received. The main CPU (21) ensures one of the voice channels as an ensured voice channel by carrying out an automatic answering for the incoming call signal when the user does not answer to the incoming call signal within the predetermined time interval. The radio transmission/reception section (24) transmits the current area identification signal stored in the main RAM (22) on the ensured voice channel.
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