| 摘要 |
PURPOSE:To transmit a non signal state to a transmission line without use of an expensive component by switching a signal from a wiring to a specific signal when the wiring is in non signal state and generating a non-signal state to the wiring when the received optical signal is the specific signal. CONSTITUTION:When a cable 3 reaches a non-signal state and an output signal 21 of a retiming unit 5 is not changed, a detection unit 7 detects it. Then a signal 22 is used to inform the state change to a switch 8 and a low frequency generating unit 6 and a low frequency signal resulting from changing forcibly the signal 21 at a prescribed period, that is, a silence signal 23 is started to be outputted. The switch 8 selects the input signal 24 to the optical transmission unit 9 from the signal 21 to the signal 23 and the unit 9 transits from the data signal transmission state into the silence signal transmission state. When an output signal 25 of the optical reception unit 11 changes to the silence signal, the unit 12 of the optical reception section 2 detects it, an output signal 26 changes and the switch 13 is opened. Thus, the input signal 27 of the retiming unit 14 reaches the non-signal state. |
