Asterisk not detecting cellphone pickup (person picking up)

Running the latest version of trixbox…

Calls to landlines are running without a problem… the line rings, person picks up, call is connected.

Calls to UK cellphones (havent tried other country cellphones) are never detected when picked up, and eventually timeout as no-answer.

The timeline is like this:

  1. Asterisk places call…
  2. Cellphone rings
  3. I pick up, and say hello, because i know asterisk needs to hear something to detect the pickup
  4. I hear dead air… no audio going either way, and the SIP packets in verbose mode are still ‘RINGING’ packets rather than answer
  5. after 30 or so seconds, asterisk gives up and logs NO-ANSWER to the CDR

When i call a landline, it just works… using the same sip gateway, so i’m 99% sure it’s not a network issue, esp as we’re getting headers back from the sip gateway saying it thinks the line is still ringing.


  1. is this an asterisk problem, or a sip gateway problem?
  2. any ideas on how to fix it? I’m using

This is an example of the packets that continue to show up in the log after i’ve picked up the call (they’re identical to the packets showing up prior to my picking up the call)

SIP/2.0 180 Ringing
Via: SIP/2.0/UDP;branch=z9hG4bK2a8514a7;received=;rport=5060
From: “38837904002142” sip:38837900009142@removed;tag=as7ae27fde
Call-ID: 5442a88f1a0422b33e0875fa16986d98@
CSeq: 102 INVITE
User-Agent: voipGATE
Supported: replaces
Contact: sip:0044@
Content-Length: 0


If this is a sip gateway call, Asterisk does NOT need to hear anything, all call control is done in the signalling. It sounds as if your ITSP has a gateway problem.

you need to look at the sip debug for the whole call.


aaah… so it’s more likely their issue… makes sense as asterisk has been pretty rock-solid so far when it comes to basics like making sure calls are connected up…

I’ll raise this as an issue with the sip/pstn gateway folks at our provider.