piclist 2004\09\29\063108a >
Thread: USB <-> POTS
face BY : Nate Duehr email (remove spam text)

Ake Hedman wrote:
> With my ICD2 still out of order I have to find something else to do ;-)
>  so I started to look at the Open source PBX
> Asterix(http://www.asterix.org). This is something that looks very
> capable and interesting. We have ISDN for telephony and as a Internet
> backup here in the office so it should be easy to setup a connection to
> the server using ISDN4LINUX and the real world.
> To be able to use old POTS equipment (and wireless GAP phones) I have to
> by a card that interlace them (POTS i/f). As it seems they are all sold
> as PCI cards with different number of POTS lines. But what I would
> really like to have is an USB <-> POTS interface. When I need another
> line I just add another USB<->POTS i/f. Modular and easy to handle.
> But.... googling does not find any manufacturer of such things... Has
> anyone seen something like that?
> As an alternative. Would it be hard to build?

ISDN4LINUX would get you a data connection to the Linux box.  You'd
still need a way to get from there to the PSTN for voice calls.  I don't
think (unless I missed something in an alpha or beta release) you can
route voice calls from ISDN4LINUX into Asterisk, but I could be wrong.

Depending on the sheer number of 2-wire phones you wish to interface to
an Asterisk machine, many people wire up small offices using a FXO card
in the Asterisk box (usually more than one) to bring in standard POTS
lines and then have lots of extensions hanging off a T1 card and a cheap
T1 FXS channel bank, like those made by Carrier Access Corp.
(Disclaimer: I used to be a CACS employee long ago.)

For the cost of a "junk" PC, an FXO card (~$40 USD) or two or three for
regular POTS lines for incoming calls, and a T1 card and used channel
bank (~$450 USD or a little more), they end up with a 24 extension PBX
complete with voice mail, intelligent call routing (well, as intelligent
as the guy writing the scripts, anyway...).  Asterisk also has the
ability to link to other Asterisk boxes over the Internet (IAX2
protocol, proprietary) and/or standard SIP-based IP telephony services
or other standard VoIP PBX'es.

There are four or five companies out there (all relatively small and
just getting started with no clear "winner" yet) that will also route
real phone calls from an Asterisk box sent out as SIP calls to the
real-world PSTN.

It's a neat enabling technology for small business.  It also JUST went
to version 1.0, so it's on the cutting edge of stability and usability,
meaning... it can eat up a whole lot of your time configuring it at
first, from what I hear.

As someone else mentioned there are also a whole bunch of SIP-based
phones and SIP-to-POTS (both FXS and FXO versions available) out there
these days, VERY cheap, and it's relatively easy for a patient and
determined person to configure an Asterisk box to sit in the basement
and have a couple of phone lines running into it and to teach the
Asterisk box to "ring" the SIP-based phones over Ethernet.  If you
understand networking and such, using something like the IAXy that uses
the IAX2 protocol and delivers a standard FXS port, one could build a
setup that would allow you to plug in the IAXy to just about any
Internet-connected Ethernet jack in the world and have calls routed from
home/work/wherever you have your Asterisk box to the "extension" that
just logged into the system from a hotel room, or whereever else you are.

It's about as wide-open as your imagination right now, and that's always
neat.  Got two phone lines?  Set up Asterisk to do "follow-me" roaming
when you're not home, maybe even giving callers that option via a
menu... "If you'd like me to try to connect you to Nate live, press 1.
If you'd like to leave a message, press 2."  Teach the Asterisk box your
cell phone number, but never have to give it out to anyone, etc.

I've been playing around with the standard SIP-to-FXS devices to try to
link 2-way radio systems together.  What would be ideal is a cheap
SIP-to-E&M device, but I haven't seen any in low port-densities yet.
Ideally I need a two-port device.

Nate Duehr, @spam@natespamspamspam_OUTnatetech.com
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