| 摘要 |
PURPOSE:To remove an access switch dedicated to a channel test from a subscriber circuit and to make the subscriber circuit small in size and economical by returning the detection results as to a DC loop circuit from a DC monitoring circuit to a testing device. CONSTITUTION:Return switches 113 and 114 are provided at connection points between a speech current supply circuit 11 and a two-wire/four-wire converting circuit 13 in the subscriber circuit 1'. Consequently, the normalcy of a return channel passed through the channel 31 in a digital switch network 3, digital encoding circuit 14 in the subscriber circuit 1', and two-wire/four-wire converting circuit 13 is confirmed without using the access switches, and the output of the DC monitoring circuit 12 is returned to the testing device 2' through a gate 15. Consequently, the normalcy of speech current supply functions of the speech current supply circuit 11 and DC monitoring circuit 12 and a monitoring function for DC loop circuit formation is confirmed. |
