[asterisk-users] OT - How does the blind transfer function work on Snom-870?

John Kiniston johnkiniston at gmail.com
Thu Mar 5 10:22:15 CST 2015

Take a look at two variables you can set on your SIP peer.


You should be able to use this syntax in your sip.conf


You can then create the logic you need in your dialplan to change the ring
using something like

exten => _XXX,1,SIPAddHeader(Alert-Info: Ring1)

Or you could modify your extension macro and have a test there to see if
the call has been blind transferred.with

ExecIf($[${LEN(${BLINDTRANSFER})} > 0 ]?SIPAddHeader(Alert-Info: Ring1))

On Thu, Mar 5, 2015 at 8:43 AM, James B. Byrne <byrnejb at harte-lyne.ca>

> On Thu, March 5, 2015 09:56, Ruben Rögels wrote:
> >
> > Hi again,
> >
> > I'm glad to hear that I provided a somehow useful answer.
> >
> > Unfortunatelly, I don't know these details.
> > If you wasn't lucky consulting the snom docs, maybe the snom support
> > can be helpful with information about the exact implementation
> > details.
> >
> > You also could use "sip debug" on asterisk to check what's going on
> > when pressing the transfer button vs. what's happening when using
> > "##" via DTMF.
> >
> > Are you forced to get the transfer information from the SIP
> > signalling, or can you use AMI events for example? I think
> > this would be possible if asterisk is configured to stay in
> > the media path, so re-inviting is handled over asterisk itself
> > and therefore detectable with AMI events.
> >
> I am working with a FreePBX12/Asterisk11 setup.  Asterisk stays on the
> path (B2B) and there are no peer-to-peer re-invites.
> What I am trying to do is to get our Snom870s to use a distinctive
> ring tone when external calls are transferred internally.  I have an
> extension context override that detects the origin of calls and
> assigns a distinctive ring to each based on "${CallerIDNum}".
> But when a call is transferred then the tone does not change since the
> CallerIDNum does not.  An external original call always rings as if it
> were coming from the outside (which it is but transferred calls have a
> different handling procedure than unanswered calls).  I need some way
> to distinguish when the call has already been answered at least once
> without changing the CallerID.
> I am not worried about attended transfers since then the internal ring
> tone is what should be used and that is what happens now.  I just need
> to deal with blind transfers.
> What I have now is:
> 1. Outside call => ring1
> 2. Internal call => ring2
> 3. Transferred call => ring1 || ring2 (depending on 1 or 2)
> What I want is:
> 1. Outside call => ring1
> 2. Internal call => ring2
> 3. Transferred call => ring3 (regardless of 1 or 2)
> If everything went though ## then that would be simple enough.  The
> trick is that most (all) users employ the transfer button and the
> touch screen to forward calls using blind transfer.  But whatever
> method they use to transfer I want the transfer ring tone to be the
> same, albeit different from the one used for a new incoming call.
> If the transfer is done using a sip message then that should be doable
> as well.  I just have to discover what the message is.  If someone
> already knows and would care to share the information then that would
> be helpful.  Otherwise wireshark and debug will eventually reveal it.
> I may not know what I am doing. But, at least I know that I do not
> know what I am doing.
> --
> ***          E-Mail is NOT a SECURE channel          ***
> James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
> Harte & Lyne Limited          http://www.harte-lyne.ca
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