[asterisk-users] alarm POTS lines

[Ryan Wagoner]

On Thu, Dec 2, 2010 at 11:58 AM, Jeff LaCoursiere <jeff at sunfone.com> wrote:
>
> Hi,
>
> I've brought this up in the past and there was a good discussion - am
> wondering if there have been any new developments.
>
> Our dialtone service, like I am sure is true for most ITSPs, touts the
> ability to drop your POTs lines for significant savings.  For businesses
> we have a low-cost Atom based PBX and a "fax relay" setup locally with
> hylafax/iaxmodem to solve that issue, and it is working very well.  We
> don't however, have a solution for their alarm lines.
>
> The problem is of course that modem calls over VoIP are flaky at best.
> Even though these alarm calls are low baud rate, when we test with the
> alarm company we only pass about 30% of the time (ulaw from customer site
> to our central switch, then out a T1).  To be fair there is no QoS on
> their Internet links yet, and that certainly plays a role.
>
> But it seems to me that there should be a solution much like our "fax
> relay", where we literally accept the fax call over the local LAN, produce
> a PDF file, transfer it to the central switch which then dials it back out
> over a T1.  In that case the only "modem over VoIP" is on their local LAN,
> which has performed well for us.
>
> I would love to see a DSP "modem" that could answer an asterisk channel,
> send the data stream over TCP to some remote asterisk, which could then
> "relay" the stream by making an outbound DSP modem call on a PSTN trunk.
> Has anyone attempted anything like this?
>
> As an aside, since the recent thread on Seagate Dockstar installs, I have
> several running.  This would be the perfect platform for the "relay" on
> the customer end, being so ridiculously cheap (I bought three for $30
> each, plus 3 $10 4G USB sticks).
>
> So hoping this will spark some comments on the concept in general, and
> really hoping someone has actually tackled something similar.  It could
> open up a nice niche for even residential customers with expensive POTS
> lines dedicated to alarm systems.
>
> Cheers,
>
>
> --
>
> Jeff LaCoursiere
> SunFone
> jeff at sunfone.com
>

Alarm panel communication, at least with Ademco, is done only with
DTMF. When I tested the Asterisk AlarmReceiver application I found
that the DTMF tones were so short they weren't always recognized by my
ATA in RFC 2833 mode. Changing it to inband DTMF worked better, but
then I was having issues with the AlarmReceiver application.  Have a
look at the below link, which touches on alarm panel communicates.

http://www.voip-info.org/wiki/view/Asterisk+cmd+AlarmReceiver

Since the communication is done with short DTMF it only takes a few
seconds once the remote end answers to relay the message. This is not
the same as modem communication when sending a fax.

At least for alarm communication the solution would be an ATA that can
correctly recognize and translate the DTMF to RFC 2833. Then it is up
to the remote end to correctly translate this back to DTMF to send
over the T1. The below link explains the different DTMF modes
supported by Asterisk.

http://www.voip-info.org/wiki/view/Asterisk+sip+dtmfmode

Ryan