| 摘要 |
PURPOSE:To make a return test of an object data channel independently through a return testing circuit as well as speech channels by providing a means which selects the object data channel among speech channels and a loop path to which the transmission channel and reception channel of the selected data channel are connected. CONSTITUTION:The selecting circuit (SEL)121 which selects a D (data) channel to be tested among connected speech channels and the loop path 122 to which the transmission channel and reception channel of the selected D channel are connected are provided in the return testing circuit 12. A D channel testing circuit 122 sends transmit packet data ps to the transmission channel of the object D channel. This transmit packet data ps is transmitted to the return testing circuit 12 through a multiplex control circuit 8 and a network 7, returned to the reception channel through the loop path 122, and sent back to the D channel testing circuit 113 in a maintenance testing device 11 through the same D channel as the transmission channel. |
