| 摘要 |
PURPOSE:To detect a local system down without decreasing the number of pieces of terminal equipment connections by providing a system down decision part on a repeating amplifier. CONSTITUTION:In case a signal line 3a is shortcircuited, since the output of the response detecting part 43 of the repeating amplifier 4 keeps in a 'H'-level at all time, the system down decision part 45 detects it, and outputs a local system down signal Vd. This signal Vd is inputted to a signal processing part 42 and to a response transmitting part 44 via a response gate 46, so that a local system down signal Vd' made of current mode signal is outputted during the SO period of a start signal, and that the transmission of a response signal Vb from the repeating amplifier 4 is stopped during other periods. Accordingly, the system down detecting part of a central control unit 1 can recognize the local system down by checking the output of the response detecting part 43 during the S0 period of the start signal of a transmission signal Vs, and the signal processing part executes the processing corresponding to the local system down.
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