asterisk users - Oct 2005 - FXS Disconnect Supervision (Kewlstart / Open Loop Disconnect)

Hello,
 
For the past week or so, I've been looking everywhere for information
about disconnect supervision and have come to the following conclusion:
there is a plethora of information available on RECEIVING disconnect
supervision signaling via an FXO port on analog cards like Voicetronix
and Digium.  However, there is very little available about providing
disconnect supervision signaling via an FXS port.  
 
Here's some general (the most comprehensive I've found) information:
http://www.sandman.com/cpcbull.html
 
The upshot of this is that I'm trying to connect a Norstar MICS system,
which has FXO analog ports, to our new Asterisk system, using FXS ports.
The Norstar only recognizes disconnect supervision and, otherwise, will
not free up the line unless explicitly told to do so, so it's necessary
for me to provide that signal from a FXS port on a card that's ready for
use in Asterisk.  I've already used one card and, at least until now,
have not had any success.
 
Can anyone provide any information or experience regarding this or
advise me on another solution?
 
-David Stude
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On Monday 31 October 2005 08:37, David Stude wrote:
> The upshot of this is that I'm trying to connect a Norstar MICS system,
> which has FXO analog ports, to our new Asterisk system, using FXS ports.
> The Norstar only recognizes disconnect supervision and, otherwise, will
> not free up the line unless explicitly told to do so, so it's necessary
> for me to provide that signal from a FXS port on a card that's ready
for
> use in Asterisk.  I've already used one card and, at least until now,
> have not had any success.
I interfaced our Norstar MICS trunk lines to a cheap-ass Carrier Access Access 
Bank I with FXS ports and I *never* had any issues with the MICS not dropping 
the trunk line when the call was completed.  I now use a DTI+PRI keycode and 
do the Asterisk<-->Norstar connection with a PRI but it worked fine in the
original case.

Basically if you tell Asterisk to use KewlStart signalling on the line it will 
send the CPD bit pattern on to the line, but if the channel bank/remote 
equipment doesn't know what to do with it, nothing will happen.  This is the
case with the AB1 and AB2.  The Carrier Access Adit600 knows how to sense and 
send CPD so it's not an issue there, and the TDM FXS modules I believe do 
handle the CPD state properly.

Actually I just checked the wctdm driver and it does seem to support polarity 
reversal when instructed from Asterisk, which is what would happen when 
KewlStart signaling is selected.  (wctdm.c, wctdm_ioctl() function, 
ZT_SETPOLARITY case if you're curious.)

Have you actually tried this, or are you raising potential concerns?

-A.