[Asterisk-Users] BLF for POTS lines via SIP

[Shawn Iverson]

Greetings,

I am looking into the possibility of whether it would be possible to
create an indicator light for a zap channel over SIP, possibly via SIP
presence or some other means.  I am open to alternatives if anyone has
suggestions.

I am wanting to do this as a stop-gap measure as I help transition a
school system from old, disparate Toshiba PBXs to VoIP.  Unfortunately,
a PRI will not be available right away, and neither will the ability to
offload calls onto POTS lines at another location.  It also will not be
possible to add additional POTS lines at this time.  Most sites have
between 2-4 POTS lines available, shared between 20-30 staffmembers.
Each of these people must contend for one or more of the lines, and
having an indicator on the phone that a line is in use would save users
from finding out until after an outside number is dialed that a line is
not available.

I have found information on both the Wiki and the mailing list archives
that BLF is possible with SIP extensions via the use of SIP presence,
using the hint command, on phones such as the Snom.  I have also found
that it is possible to monitor zap channels in a call manager.  Perhaps
a mix of the two is possible?  Please note as well that only a portion
of the phones would be near a computer.

If not, perhaps some other method of contending for the lines is
possible, maybe with an auto-retry and dial-back once a line becomes
available?  

--

Shawn Iverson
Technology Associate
MCSA, Linux+, Network+, A+
New Castle Community School Corporation
shawn at nccsc.k12.in.us