How to force pickup of ringng SIP phone

I have linksys SPA942 receiving calls from a queue and a Java application talking to the asterisk server using the AsteriskJava library. When call comes in to the phone the application shows that the phone is rining

Does anyone know how I can get my application to force the phone to pick-up the ringing call?

I know there is a SIP Header option that I can use to have the phone auto-answer calls
SIPAddHeader(CALL-INFO: sip:;answer-after=0
But is only useful prior to dialling.

In this case the call is coming from a queue, and is currently ringing.

Anyone have any thoughts?

Andrew.

This going to be phone specific, but it is most unlikely that you can do it after dialing, as the only thing the caller is allowed to initiate at that point is cancellation of the call.