Are they in a room with echo dialing while on speakerphone? On 3/18/2011 1:32 PM, Jay Hennigan wrote:
We are having some issues with doubled DTMF digits from a customer dialing into conference bridges, etc.
Scenario: Shoretel PBX -> PRI -> Adtran TA900 -> SIP trunk. We are using G711/RFC2833.
The problem is intermittent, about 5% of calls or less, read-back of received digits shows occasional doubled digits, almost always DTMF "1".
We were able to duplicate the issue with the Shoretel system going out a conventional TDM PRI as well, but the customer and the conferencing vendor and the customer tend to blame the problem on "the VoIP system". It is very intermittent and DTMF works fine most of the time.
The Shoretel itself sends only a short burst out the PRI regardless of the length of time the DTMF key is held.
Comments from voice users on the receiving end are that the Shoretel caller's voice seems "hot". The Adtran has settings to adjust level on FXS but not on PRI. The Shoretel does have adjustments, presently set to 0 dB.
It is my recollection from the old Bell/Mitel days that there should be padding on T1/PRI trunks but I can't find a spec. From memory I want to say -6 transmit and -3 receive but Google is failing me on finding this documented. Is there a standard loss/level best practice for this?
The fact that the issue occasionally occurs on the TDM trunks leads me to think that the SIP RFC2833 conversion is not to blame and that perhaps there is acoustic coupling between the tone played out the phone's speaker being picked up by the microphone that padding would help.
Any suggestions would be appreciated.
-- Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV _______________________________________________ VoiceOps mailing list VoiceOps at voiceops.org https://puck.nether.net/mailman/listinfo/voiceops