| 摘要 |
PROBLEM TO BE SOLVED: To reduce a power consumption by decreasing unnecessary control signal retrieving operations. SOLUTION: A communication system of a radio telephone comprises a plurality of radio base stations 201 and 202 connected to a public system, a master unit 203 connected to a self-employed system, and a slave unit 10 connected to any of the stations 201 and 202 and the unit 203 in a time division multiplexing radio transmission line and capable of transmitting and receiving voice and control data. In this system, the unit 10 waits for any one system of the public system and the self-employed system. When the unit 10 is disposed in a region outside of communication range of another system, if a prescribed value or more of change does not exist in a receiving electric field value stored each time a control signal of the waiting system is received, the unit 10 does not retrieve the region outside-of-communication range system.
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