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We just had an issue where we change the routing of calls to now route through SIP circuits, through an SBC.
We have announcements in our environment that were ALL working prior to changing this routing.
After the re-route, several of these were failing.
What we discovered is that the BYE from the CM was being sent before the last DTMF of the wav file was received by the SBC. We never saw it hit the SBC, just the second to last digit, a 200OK and then the BYE.
We found that this was only happening for wav files that the DTMF was the very last thing played in the announcement with no silence after the last DTMF. If we added 2 seconds of silence to the end of the wav file, then the last digit would reach the SBC and the carrier would send the BYE once it took back the call.
Since there are a lot of announcements we would have to review, potentially a lot to modify and then upload back into the system, we found 2 different ways you can fix this.
If your line to play the transfer connect announcement is just an announcement XXXX line, then after that line put in a step: wait-time 2 seconds hearing silence.
If your line is announcement, or disconnect after announcement, you can change the line to a collect 1 digits after announcement XXXX. This is what we chose because it was easier and didn't add a line to the vector (in-case your vectors are tight on space). In addition, it retains the announcement number for you so you "can't" make a mistake and fat-finger the number back in.
The collect step also uses your inter-digit timeout that allows for the time needed for the carrier to get the last DTMF digit and the carrier to take back the call. This doesn't add any time to the call as it will disconnect as soon as the carrier sends the bye.
- Stinney
“The man who asks a question is a fool for a minute, the man who does not ask is a fool for life.” - Confucius