| 摘要 |
PURPOSE:To avoid the reliability and utility of a system from being lost, due to unnecessary reception switching operation, by inhibiting the reception switching operation when the line is interrupted. CONSTITUTION:A reception signal from an antenna 31 passes through the 1st changeover switch 32, and enters an existing receiver 11 and also a spare receiver 21 in a level lower than the reception input at the existing receiver by several dB. An output signal of the receiver 11 is given to a device output terminal 35 through the 2nd changeover switch 34. An electric field detection signal picked up from an intermediate frequency amplifier 16 enters a squelch circuit 17. A device control section 33 monitors the squelch signal of the existing and spare side, and if the squelch for the spare side takes place earlier, it is discriminated as the interruption of line, no changeover is done, and if the squelch for the existing side happens earlier, it is discriminated as a failure of the receiver 11, to change over the changeover switches 32 and 34. |
