Step 1 Use the LMT to trace TUP messages on the U1980.
Step 2 Analyze the ACM message returned by the U1980 to the peer end. It is found that the user idle indicator is not specified.
The ACM message is as follows:
Address complete message (ACM)
00010100 H1H0: ACM
00000000 message indicator
------00 address complete signal type indicator: address complete signal
-----0-- user idle indicator: not specified
----0--- incoming call echo suppression indicator: incoming call echo suppression not contained
---0---- call transfer indicator: no call transfer
--0----- signal channel indicator: any channels
00------ reserved: 0x0
The ACM message returned by the U1980 does not indicate whether the called party is idle. As a result, the RBT cannot be played. The RBT heard by the calling party is played by the U1980.
Step 3 Set software parameter 387 to 1. The fault is rectified.
config softargu type 387 value 1
Software parameter 387 is used to set calledstatusind of the ACM message in SS7 signal.
0: Not specified (default)
If the called party is busy, the corresponding announcement is played.