| 摘要 |
PURPOSE:To improve communication efficiency by allowing a transmission line changeover switch to use connection circuit between standby switches to apply loopback to a signal from a receiver side standby switch to a sender side active line switch, thereby simplifying the loopback function by changing over the transmission line. CONSTITUTION:A signal inputted to a terminal 2a of a sender side active circuit switch 1a is outputted to a sender side transmission line 10a at normal transmission/reception and a signal received at a terminal 6a of a receiver side active circuit switch 5a is outputted from a terminal 6b. Moreover, a signal inputted to the terminal 2a of the switch 1a at circuit changeover is inputted to a terminal 4c of a sender side standby line switch 3 from a terminal 2c and outputted to a sender side standby transmission line 12. Then in case of loopback, a signal received by a switch 5a via a receiver side transmission line 11a is inputted to a terminal 8c of a receiver side standby line switch 7 from a terminal 6c and inputted to a terminal 4a of the switch 3 via an inter- standby line switch connection circuit 9 and a terminal 8a and further inputted to the terminal 2a of the switch 1a from the terminal 4c.
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