[Freeswitch-users] Strange DTMF Tones On Inbound Calls

Daniel Knaggs Daniel.Knaggs at realitysolutions.co.uk
Tue Apr 3 19:52:21 MSD 2012

Audio was captured using “record_session” where it didn’t appear in the audio by “ear”.

“ftdm dump” displays details about the span I tell it to: -

span_id: 1
chan_id: 1
physical_span_id: 1
physical_chan_id: 1
physical_status: ok
physical_status_red: 0
physical_status_yellow: 0
physical_status_rai: 0
physical_status_blue: 0
physical_status_ais: 0
physical_status_general: 0
signaling_status: UP
type: B
state: DOWN
txgain: 0.00
rxgain: 0.00
cause: NONE
session: (none)


From: freeswitch-users-bounces at lists.freeswitch.org [mailto:freeswitch-users-bounces at lists.freeswitch.org] On Behalf Of Michael Collins
Sent: 03 April 2012 16:31
To: FreeSWITCH Users Help
Subject: Re: [Freeswitch-users] Strange DTMF Tones On Inbound Calls

On Tue, Apr 3, 2012 at 8:17 AM, Daniel Knaggs <Daniel.Knaggs at realitysolutions.co.uk<mailto:Daniel.Knaggs at realitysolutions.co.uk>> wrote:
Update, it would appear (so far) that this has worked.

I can see in the log numerous “Rogue digit: DTMF 'A' received” entries (and also for “C”) and I’ve asked the users if they have heard any more tones and they haven’t.

Thanks, Michael.   So we’ve managed to work around it, but how can I track down what is generating these tones to begin with?  Is my earlier spectrum analysis of a call any good?

I don't think we ever truly answered the question of whether or not these rogue digits are phantoms. Remind me: how did you capture the audio on which you did the spectrum analysis? I recommend using ftdm dump, which is nice because it captures raw audio in either direction, and if I understand correctly it is what's "on the line" - if those rogue digits are coming from the other end they'll show up in the raw dump. If those digits are not in the raw audio then most likely you're looking at a false positive from the DTMF detector, in which case you've got a bit of a conundrum because you've got hardware from Digium and software from Sangoma and you need to figure out where to begin looking...

BTW, feel free to keep the BDA's in there and just add your transfer digits to the digit action realm and you can avoid using bind meta app. BDA is the preferred method nowadays.


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Daniel Knaggs

Software Developer

        Reality Solutions Ltd, 1 Global Business Park, Hamburg Road, Kingston upon Hull, East Yorkshire, HU7 0AE
Tel: 01482 828000 / Fax: 01482 373100
Daniel.Knaggs at realitysolutions.co.uk<mailto:Daniel.Knaggs at realitysolutions.co.uk>

Sage Accredited Business Partner serving businesses in Yorkshire & Lincolnshire

[cid:imagee8ba2d.PNG at 2a4e8ae6.4a92bc17]

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