| 摘要 |
PURPOSE:To avoid disabled transmission/reception by providing a transmission/reception section for satellite line making transmission via a satellite, a transmission/reception section for a ground line and an intensity measuring means of a signal received by both the transmission/reception sections and making transmission/reception with the transmission/ reception section whose reception level is higher. CONSTITUTION:When a transmission/reception section 2 or 3 makes transmission/reception by the control of a central processing unit 1, it judges whether or not communication is enabled at a coordinate detected by a position detection section 9 based on the information from a map information reproducing section 10. When the coordinate is a position where communication is enabled through both a ground line and a satellite line, a signal intensity discrimination section 8 judges the reception level of the transmission/reception sections 2, 3. The transmission/reception section offering more excellent transmission is selected. Moreover, when only one of the transmission/reception sections is available for the communica tion, the transmission/reception section enabling the communication is automatically selected. Furthermore, it is judged that the communication is disabled of both lines, after the communica tion is in standby for a prescribed, the positioning measuring is again tried and the communica tion timing is delayed. In such a manner, an event of disabled transmission/reception is avoided by making communication through an optimum transmission line in response to the position of the travelling object.
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