[VoiceOps] PRI loss/level settings - DTMF issues

Lee Riemer lriemer at bestline.net
Fri Mar 18 15:30:45 EDT 2011

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
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