Ringback on blind transfer

Hi all.

I have a problem with ring-back tones while making blind transfer on sip extension.

I have SIP extension A registered with ekiga softphone. This extension calls other extension B that answers the call and makes blind transfer to extension C. Once transfer is done, A hears silence until C picks up.
I tried to send “Ringing 180” message to sip client of A to force it play ring-back, but it did not help.

Can any one help me with this?


How did you initiate the transfer. In particular was it a SIP or Asterisk features transfer.

Asterisk will not pass a REFER to party A; it will perform the switching within itself. I don’t know how you could send 180 Ringing to A, but it would be out of state.

Asterisk will need to fake ringback itself, inband.

Also, which version of Asterisk?

I use asterisk 1.2.

It doesn’t matter how transfer is done. If party B is SIP extension, it sends REFER to A.
In both ways I have the same result - A hears silence until C answers.

I suspected that my “180 Ringing” is out of state and is simply ignored by SIP client, but I had no other idea.

I’d like to know if is there a way to make ringback except sending it inband?

1.2 is no longer supported and I don’t know how it handles blind transfers. 1.4 and 1.6 both field the REFER for a SIP transfer, and bridge party A and C without passing the REFER to party A. There is no REFER involved, in 1.4 and 1.6 for a features transfer.

Ok, but how 1.4 and 1.6 implement ringback to party A?

Asterisk generates the tone, in band.