To enhance the economical efficiency for a caller in a communication system where a plurality of communication networks with different communication systems are intermingled.
An integral communication network 22 is built up with a personal digital cellular PDC communication network 18, a personal handy phone system PHS public communication network 19, and a PHS private communication network 20 in mixture. When a portable telephone set 1 registers its position to the PHS private communication network 20 (position registration), an incoming call switching signal is transmitted to an integral communication network 22 (incoming call changeover). On the occurrence of an incoming call request from the PDC communication network 18 to the portable telephone set 1, the integral communication network 22 receives an incoming call switching signal to transfer the incoming telephone number from the PDC telephone number to a PHS private telephone number. Thus, the portable telephone set 1 receives the PHS private communication network 20 (call reception). Since the communication charge using the PHS private communication network 20 is not accounted on a caller, the communication charge is reduced.
KAKEHI TORU
SAKAI HIROSHI
YAMAZAKI TORU
INOUE AKIRA
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