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

[akohlsmith-asterisk at benshaw.com]

Hi Andrew,

Thanks for responding.  Yes, I noticed that some code *seems* to support
this.

I started with a Voicetronix Openswitch12, which has, even in its driver
code, no support for anything resembling kewlstart.  After figuring out that
the MICS seemed to respond to opening the circuit for a short time, I tried
to program a "flash" into asterisk (and then tried to write simpler code to
interface with their driver) and found that doing anything with flash or
"on/off hook" status while the card was in FXS mode made the port totally
unstable.  I've been dealing with someone at Voicetronix and, after the
usual "WHY would you use FXS to interface with a PBX?!," he seemed
helpful...until I told him that I figured that there was absolutely nothing
that I could imagine, software-based, that I could do to get around it.

After my boss caught wind of it, he's now trying to control the situation a
bit.  We ordered a Digium card AND now he wants to create a circuit with as
many relays as we have lines and trigger that using signals from the
parallel port.  I'm extremely hesitant to go that route for obvious reasons.
I'm hoping the Digium card works, but if it doesn't, I'm stuck either
returning a lot of hardware or going to get solder burns.

-Dave


-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Andrew
Kohlsmith
Sent: Monday, October 31, 2005 8:51 AM
To: asterisk-users at lists.digium.com
Subject: Re: [Asterisk-Users] FXS Disconnect Supervision (Kewlstart /
OpenLoop Disconnect)

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.
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