[asterisk-dev] SIP Phone Conference from Asterisk.

[Eric "ManxPower" Wieling]

md wrote:
> Hi,
> Is possible put in conference a sip phone where there are two calls (one active and the other held) from Asterisk? Is there any SIP header to activate the conference in a SIP phone remotly?
> 
> El escenario es:
> 
> 1. SIP A calls SIP B: call 1
> 2. SIP A calls SIP C: call 2 --> call 1 held; call 2 active
> 3. ASTERISK APPLICATION notify SIP A for put call 1 and call 2 in conference.
> 
> Is the step 3 possible? Is there any SIP header to indicate to a SIP phone 

Step 3 is not possible in the way you describe.  However, many, many SIP 
phones support it within the phone.  Asterisk just sees two calls.  The 
phone does the audio mixing inside the phone.  Polycom, Cisco, and 
SIPura phones do this.  I'm sure most other SIP phones also do it in 
this way.  This feature may be called "3-Way Calling".