In a communication process, trunk line butting interconnection errors (including cross-connected lines and loopback) in TUP (Telephone User Part) or ISUP (Integrated Services Digital Network User Part) results in cross talk, mono-directional connect, and bidirectional disconnect, etc. in sessions. Usually, the trunk errors need to be located with methods such as loopback, pulling E1, or specifying a circuit for Call-Testing.
However, in TDM (Time Division Multiplexing) A-interface circuits, errors may only be checked with methods including loopback, pulling E1 and specifying a circuit for a Call-Testing. Suppose that there are 10 E1 lines between two NEs (network elements), the 10 E1 interfaces (No. 1-10) of NE A need to connect to the 10 E1 interfaces (No. 1-10) of NE B; first, the person responsible for the maintenance of NE B performs “loopback” or “pulling/plugging E1” for E1 interface 1, making the E1 connection “disconnected” or “connected”; then, the person responsible for the maintenance of NE A checks whether a corresponding E1 “disconnected” or “connected” occurs at E1 interface 1 of NE A, to determine whether the E1 connection is correct. All E1 ports are checked by repeating the process. If the “specifying a circuit for Call-Testing” method is used, the person responsible for maintenance may perform actual Call-Testing after E1 is connected, and make the call occupy the channel for testing E1 by the function of “specifying Call-Testing; and if the session is normal, it shows that the E1 connection is correct.
It is apparent that the above solutions are troublesome and may not locate circuit errors quickly and conveniently; therefore, the maintenance cost is increased.