[asterisk-users] Sip Header Help

[voip crazy]

Dear List:

I need to make a sip phone (spa942) answer a call but the phone must
no ring. The user only has to show the callerId on the phone screen
without any sound.

How could I make that in asterisk? I tried to use Sip headers but I do
not know how must I say the phone don't ring when received, only shows
the callerID of the call.
How could I do that with sip header?
Which sip header should I send the phone to change the callerID of the call?

Do you know any other way to ghet that.
Any clue will be wellcomed.

Thanks for your answer.

VoipCrazy.