[asterisk-users] Setting up only one caller at a time

[Mike A. Leonetti]

A little bit of a strange request.

Basically I want all calls that go to one user go to voicemail
immediately if the user is on the phone.  The user is using the Linsys
SPA941, and even though he can be on the phone, calls will still ring
his phone.  I tried disabling the rest of the "lines" on the phone so
there was only one and yet it still rings the phone when he is on it. 
The call comes in through a special DID.

So is there a flag to set if the user is current on the phone or if
there is already a call on the DID?