[VoiceOps] PRI loss/level settings - DTMF issues

[Jay Hennigan]

On 3/18/11 12:30 PM, Lee Riemer wrote:
> Are they in a room with echo dialing while on speakerphone?

Sometimes, but I've been able to duplicate the failure on a handset.

An analog phone on an FXS port on the Adtran works perfectly.

> 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
> _______________________________________________
> VoiceOps mailing list
> VoiceOps at voiceops.org
> https://puck.nether.net/mailman/listinfo/voiceops


-- 
--
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