| 摘要 |
<p>PURPOSE:To perform hitless switching by providing a buffer circuit which absorbs the step change of phase it the time of hitless switching and an asynchronous detecting circuit which masks asynchronous detection for a certain time only at the time of hitless switching. CONSTITUTION:When the hitless switching operation is started, an asynchronous detecting circuit 22 detects the phase step as the asynchronous state until the phase of the clock of a buffer circuit 21 coincides with the phase of the input clock of a line to be switched. A switching signal 106 is supplied to the asynchronous detecting circuit 22 not to output a device fault signal 107 till the end of absorption of the phase step, thereby controlling the asynchronous detecting circuit 22 to prevent the switching of a receiving-end switching circuit 20. Thus, hitless line switching is performed by a hitless switching circuit 15 without switching the receiving-end switching circuit 20 even when a phase difference between a current line signal and a stand-by line signal exists.</p> |
