To reduce a case where communication is impossible and to select a communication means which is always efficient by measuring a distance between a mobile object and a central management device prior to communication, selecting a radio communication means whose priority is the highest among the radio communication means realizing communication and executing communication.
Plural communication means 13 are provided between a mobile station 1 and a central management device 2. Any communication means 13 can execute reception. A communication means selected by communication controllers 12 and 21 execute origination by the position of a mobile machine and the number of retry times. Thus, a system for automatically selecting the optimum communication means is constructed. When a distance between the mobile station 1 and the management device 2 is short and any installed communication means is predicted to be communicated, simple radio whose communication frequency can be improved, whose running cost is inexpensive and which does not require a license is preferentially selected. Thus, the communication means which is always efficient is selected and communication can be executed.
YAMADA TETSUSHI
KURANASHI KENTARO
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