| 摘要 |
PURPOSE:To prevent the mixing-in of signals of other current lines at a swiching time to an auxiliary line by inhibiting the transmission of transmission-end parallel release instructions until the operation of a transmission-end parallel switch is confirmed by the receiving-end when a line trouble has been restored in a short time. CONSTITUTION:When a trouble has occurred in current line 101, a relief operation is started by current line pilot detector 107, transmission-end parallel signal oscillator 111, transmission-end parallel signal detector 112 and transmission-end parallel switch 103 in order. Then, the signal of line 101 is transmitted through auxiliary line 102, and the current line pilot signal is detected at time T2 after trouble occurrence by detector 109 provided in the receiving-end of line 102, thereby confirming the operation of switch 103. Then, even if the trouble of line 101 has been restored at time T1 (T1<T2) after trouble occurrance, the transmission of transmission- end parallel instructions of line 101 by oscillator 111 is continued and the transmission of transmission-end parallel release instructions is inhibited. |
