| 摘要 |
PURPOSE:To relay two areas not to be relayed by one antenna by switching selectively antennas for transmission/reception use arranged in two areas in response to the state of the area. CONSTITUTION:When no radio wave is emitted from stations in areas (1), (2), the state that the antenna in one area is used for the reception and the antenna in the other area is used for the transmission antenna, and the opposite state are switched alternately. When an output of a prescribed level or over exists from a reception circuit 4, a switch changeover timing circuit 6 stops its oscillation by the output of a threshold detection circuit 5 and switches SW1, SW2 hold the connecting state. Thus, the state making transmission/reception from the area (1) to the area (2) or from the area (2) to the area (l) is formed.
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