[Asterisk-Users] one extention, multiple phones

[John Todd]

At 5:11 PM -0700 on 7/31/04, Sean McKay wrote:
>On Sat, 31 Jul 2004, Paul Mahler wrote:
>
>>  You can easily ring different phones at the same time within the dial
>>  command. For example,
>>
>>  SIP/4024&${PRITRUNK1}/16505551212&${PRITRUNK1}/14155551212
>>
>>  A blind transfer will move the call to the next phone. Or you can park the
>>  call.
>
>  That's not what I want to do. With a traditional PBX or PSTN setup I can
>have more than one phone sharing the same extension. What I want to do is
>to be able to have one extension (or line) on say 3 phones. When I pick
>up the phone on one, the other two are alerted that the line is engaged
>and should give a visual indicator on the screen that the line is in use.
>Say I want someone to join in on the conversation, I'd rather much have
>them be able to just lift the receiver and begin to talk rather than have
>to do conferencing.
>
>  This is done on PSTN (normal home phone), and I've seen it done on PBX's
>such as the AT&T Merlin and NT Meridian systems. Since the application I'd
>be setting up is basicly upgrading from PSTN to VOIP I'd like to keep that
>feature of being able to share a call (w/o conference) or pick up a call
>on another phone without having to use transfer (blind or regular).
>
>  Also I'd like to say I believe this is possible with the CCM otherwise
>how could an agent (operator) be able to monitor which extensions are in
>use with the 7960 expansion device?
[snip]

The short answer is: "No, Asterisk does not support this out of the 
box, and even if it did, Cisco phones with SIP images do not support 
this out of the box."

The medium answer is: "I have no idea if any of the SCCP (skinny) 
drivers support the 79xx phones for remote indication lamps.  I gave 
a 7914 operator console to JerJer a while back to see if he could get 
that running, but no news lately.  I have completely no clue on 
three-way (or barge-in, or shared line, or whatever you want to call 
it) with SCCP."

The long answer is: If you're marginally handy with C and have some 
spare time, you might be able to do this with some of the SIP phones. 
The Polycom IP500 and IP600 support the SUBSCRIBE/NOTIFY message 
transmissions for indicator lamps, which seems to 
almost-sort-of-maybe supported in Asterisk, but not quite.  I haven't 
had time to experiment with those phones enough with Asterisk to see 
what would be required to make it fully operational, and I doubt I'll 
have any time to do it in the near future, but  you could buy one 
yourself and see what you get running.   Once you've figured that out 
and corrected *'s code for presence and indicators, it should be a 
short journey to create a new channel type that represents existing 
channels and allows a third extension to "dial" an existing call leg, 
a la chan_local, but different.  See my discussion on the chan_multi 
idea here:

   http://www.mail-archive.com/asterisk-dev@lists.digium.com/msg04117.html

Feel free to beat your local Cisco representative around the head and 
neck with a blunt instrument and describe to them how they're losing 
the SIP battle with their (apparent) intentional crippling of the SIP 
image on the 79xx series.

JT