[Asterisk-Users] FXS Disconnect Supervision (Kewlstart / Open Loop Disconnect)

[Andrew Kohlsmith]

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.