[Asterisk-Users] Possible to display which extensions are in use on the phone's display?

[David Gomillion]

> From: Steven Critchfield <critch at basesys.com>
> On Wed, 2004-11-17 at 11:49 -0800, Tracy R Reed wrote:
>> On Wed, Nov 17, 2004 at 01:13:57PM -0500, Noah Miller spake thusly:
>>>> On our current phones (Iwatsu) we have a button on the phones for
>>>> each extension that lights up when that
>>> 
>>> This seems to be a popular request these days.  Most places I've
>>> seen call this "shared lines" I thought this was impossible with
>>> Asterisk,
>> 
>> And it seems to be something the developers are not interested in
>> supporting. Whenever someone asks about this feature they are
>> normally told that this is a feature of small-office "key" systems
>> and that Asterisk has its sights set on bigger systems so this
>> functionality is not pursued.
> 
> Correct, it isn't on a list for TODO as it doesn't scale to
> the size of an average office. Also it is only supported via
> some SIP phones and proprietary digital key set phones for
> which we will not get access to the supporting cards. So time
> is much better spent aiming for something that can be attained. --
> Steven Critchfield <critch at basesys.com>
> 

If you want to talk about features, scaling, etc., we should look what
the big commercial VoIP systems are offering.  The one that I have
experience with is Cisco's Call Manager.  We used shared call
appearances to allow our secretaries (excuse me, Administrative
Assistants) to catch their boss's calls and screen them, if they were
there.  While the "lines" were not available to everybody, shared
appearances were a very highly sought-after feature.

I agree with Steven about not spending a lot of time to make things work
with proprietary stuff.  When standards are closed, there is no
guarantee they won't change overnight with the next firmware release,
and therefore all of the code wasted.  But not all ways of handling
shared call appearances are proprietary.  

According to the Polycom IP manual, the SUBSCRIBE-NOTIFY method (RFC
3265) is supported on the phone.  Using the "hint" alluded to before, it
appears that it should allow multiple phones to view the state
("call-info" bit for call appearance state notification).  All that
remains unknown (to me at least) is if the button can be used to take
over the conversation (the "line-seize" part to ask to seize the line).
For references on this, refer to the Polycom SIP Administrator Guide v.
1.3.0, pages 31,135,111,113,117-8.

If these features are already implemented, then we need to let everyone
know.  I think this might be the "right way" to give the features people
are requesting while still preserving scalability.  In big systems, each
extension would be, well, an extension.  If someone wanted Asterisk to
act like a key system, then lines and extensions would have a one-to-one
correspondence, with a shared appearance on all phones.  A happy medium.

Thoughts?