| 摘要 |
PURPOSE:To simplify a circuit configuration by providing a frame asynchronism detecting circuit and detecting an equipment fault. CONSTITUTION:When the deterioration in a transmission quality of an existing circuit is detected, a switching circuit 101 switches the existing circuit to a stand-by circuit. Subsequently, a clock synchronized with a clock of a selected signal is formed by a VCO 103, and a switching output 15 whose syncronism establishment is decided is outputted from a retiming circuit 104. On the other hand, the output of the circuit 104 at the time of non-establishment of sychronization of a signal frame of the stand-by circuit in which the VCO 103 comes not to be synchronized, or the output 15 is gone, an equipment fault signal 20 is generated from the frame asynchronous detecting circuit 105. By a constitution in which this asychnronous detecting circuit 105 of the VCO and an signal disconnection detecting circuit are unnecessary, the constitution of the equipment fault detecting circuit is simplified. |
