| 摘要 |
PURPOSE:To transmit correctly error information of a fault generated in a relay station to a supervisory station by driving a squelch circuit with an output signal from a discriminating means for discriminating whether or not a transmission line identification signal is a designated signal inserted in a reception signal or a signal representing that the reception level reaches a designated level or below in a digital radio heterodyne relay device. CONSTITUTION:In order to identify whether a received wave inputted from a reception antenna 13 is a desired wave or an interference wave, transmission line identification signals FR-1-n included in the received wave are detected. Thus, the received wave converted into an intermediate frequency is demodulated by a demodulator 5, further a transmission line identification signal detector 21 extracts the transmission line identification signals FR-1-n to discriminate whether the extracted transmission line identification signal is a desired wave or not, and when the wave is the interference wave, the signal is inputted to a terminal 2 of an OR circuit 20. On the other hand, a signal representing that the reception input level is a designated input level or below is inputted from a terminal (a) of a DC amplifier 4 to a terminal 1 of an OR circuit 20. When any of the signals is inputted to the OR circuit 20, an output from the circuit interrupts the squelch circuit 6 and the connection between the reception section and the transmission section is disconnected. |
