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UC520 Dropping incoming SIP calls

Hi all,

I have the following problem:

my uc520 uses a SIP Gsm gateway for incoming and outgoing gsm calls.

We have no problem with outgoing calls, but when we receive the incoming calls it behaves wrong.

The incoming call is correctly forwarded to the interval UC520 IVR and when I choose an internal number the call is correctly forwarded to the right phone. The phone rings and as soon as I answer it the call is dropped within less than 1 second.

the final message i get from debug ccsip message is:

CSeq: 803 BYE

Reason: Q.850;cause=16

Content-Length: 0

IN attachment all the debug for a full incoming call.

(10 is the number associated with my IVR and 14 is the number associated to the internal phone).

Thanks anybody who can help me.



Re: UC520 Dropping incoming SIP calls

This looks like the message from the provider causing it:


NOTIFY sip:10@ SIP/2.0

Via: SIP/2.0/UDP;rport;branch=z9hG4bK6ee26321e9

From: "+393389791000" <>;tag=145ffdca

To: <10>;tag=3A0A8AF4-1EE

Call-ID: 088d61bf7a0c46fb3c08475643837de4@

Contact: <>

CSeq: 803 NOTIFY

Max-Forwards: 70

Event: refer

Content-Type: message/sipfrag

User-Agent: CM5K (706220)

Subscription-State: terminated

Content-Length: 18