| 摘要 |
PURPOSE: To make a cellular mobile radio telephone set able to directly access the radio channel of a private branch mobile telephone system without interfering a cellular public mobile telephone system by using a part of frequency channels used in a public mobile communication system as plural frequency channels in common. CONSTITUTION: A private branch exchange(PBX) 15 for a cable telephone line is installed in a private branch 0 and the radio channel is added to it. For the radio channel, a transmitter-receiver(TRX) 16 is connected to transmission/ reception antennas 18 and 19 through a booster 17, the f2 waves of strength for suppressing the interference f2 waves of a cellular public mobile system are transmitted and a mobile telephone set 20 is made receivable. The mobile telephone set 20 can be mutually connected to public system f1 waves as well. The transmission power P2 of the mobile telephone set 20 is set to a value of satisfying conditions that the ratio of the strength S2 of transmission f2 waves to the strength I2 of the interference f2 waves in a private branch service area boundary is S2 /I2 =S1 /I1 and the P2 is less than an upper limit value of not interfering the other adjacent private branches. |
