[Asterisk-Users] Extension buttons

[Chris A. Icide]

On 06:36 AM 4/23/2004, John Todd wrote:
 >Is it possible (ignoring Asterisk for the minute) for Polycom phones
 >to indicate visually (on the LCD or on a lighted "extension" button
 >or something) that a particular line is in use?  I would expect this
 >method to be via NOTIFY or SUBSCRIBE calls from a SIP
 >registrar/proxy/call handler upstream.

It appears the answer to this is yes.  In the Polycom config, you can 
define a line as private or shared.  If you define the line as shared, then 
the Polycom issues a SUBSCRIBE for the line so configured.  Note, I only 
tested this against Asterisk to see if the line would function as a private 
line with asterisk while set to shared (basically expecting asterisk to 
ignore the SUBSCRIBE).  However this wasn't the case, the line was 
non-functional with Asterisk when configured as shared.  When I had the 
phone in my hands, unfortunately I didn't have time to sniff the SIP 
traffic and see what exactly it was doing.

 >
 >Now, if the answer is "Yes", are there instructions anywhere on
 >exactly HOW that is supposed to work, so that someone can start to
 >code these methods into Asterisk?  This is one of the missing
 >features when people look at Asterisk as a PBX replacement - the
 >simple task of looking at the phone to see what incoming lines are
 >"off-hook" or what people are busy is lost, but this is a mandatory
 >requirement for office phone systems.
 >
I would suspect that it follows RFC3265 definition of SUBSCRIBE/NOTIFY, but 
thats merely a guess.  The SNOM 200 also issues a SUBSCRIBE message when 
configured to do so, however it seems to still function as a normal line 
even though it's configured for a shared style line.

Currently there is no way to add multiple sip UA entries for the same line 
in asterisk's sip.conf.  Internally, if Asterisk uses the SIP extension as 
defined in sip.conf as a unique identifier for the line, then the changes 
look to be quite significant.

I would think the first step would be to modify Asterisk to support shared 
lines in general using the SUBSCRIBE/NOTIFY method as described in the 
RFC.  Unfortunately my c skills border on non-existant and "a hack" so any 
chance of me doing this is out the window.

-Chris