[Asterisk-Users] Preventing incoming calls from ringing SIP lines

[Paul Redstone]

Hi

We're using three line SIP phones (X-lite), very nice, with Asterisk 1.2

But we want to prevent either direct incoming calls or calls from other 
extensions from ringing if the user is
in another incoming call (i.e incoming into the extension), making an outgoing 
call or even checking their voicemail.

In 1.0 the SetGroup and CheckGroup commands could do this but you have to build 
it into all parts of the dial plan.
In 1.2 these do not exist and the Set(Group type commands with GotoIf are 
supposed to be used. But I still have not seen anywhere a full example of this.
There is the call-limit setting in SIP - beautiful, works at the SIP level so 
easier than the dial plan.
BUT with this you cannot do attended or blind transfers - not sensible.

This must be a very common requirement, certainly is judging from the posts but 
in hours of searching I have not see the sort of complete solution which looks 
feasible.

Thanks and sorry if I've missed it.

Alternatively I'd be happy to use single line SIP softphones but cannot find 
one which feels good.

TIA

Paul R