To provide a communication system selection method for a portable telephone that can be smoothly and stably connected to two communication systems.
The communication system selection method comprises designating a priority communication system out of two communication systems, judging whether the phone communication is in the area of the priority communication system or not when the priority communication system is selected, and selecting the other communication system, namely a communication system other than the priority communication system, in the two systems when the judgement result concerning the area out of the range continues for more than a predetermined period. Thus, frequency of transition between the communication systems can be reduced, which achieves a stable connection.
OMORI YOSHIRO
Masashi Kudo
Yasuhisa Tanizawa
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