Having a problem with no audio in several ways during 3-party conference call from SIP phone. System: Samsung OS7200 v 4.80, MGI16 card.

I tried with Polycom IP6000 SIP phone, as well as with basic Fanvil SIP phone - same issues (so the problem is not in SIP device).

Scenario:
SIP phone (A) dials first digital Samsung phone (B): everything OK
SIP phone presses conf button
SIP phone dials second digital Samsung phone (C): everything OK
SIP phone presses conf button to join all 3 parties to conference
A -> B ok
A -> C ok
B -> A ok
C -> A no audio!
B -> C ok
C -> B no audio!

Conclusion: phone that joined conference as last can not be heard on other two phones.

Any ideas?

...with 3 IP devices even more problems

Try use the conf function code.

Polycom IP5000

Conference Call (2 Callers + the conference unit)

Press “New Call”, Dial 9 + number, Press Send (wait for caller to answer)

Press Hold

Press New Call, Dial 46 Press Send wait for call to clear

Press New Call, Dial 9 + Number, Press Send (wait for caller to answer)

Press Hold

Press New Call, Dial 46 Press Send

Press Resume to join the calls together.

It works!! Great! Thanks for help