asterisk users - Apr 2005 - Can I use Asterisk for a modified Hoot and Holler?

Hello wonderful asterisk users list.  

I have some energy traders that are currently using 2 wire
hoot-n-hollers (squawk box, always open direct line) to different
trading floors throughout the country.  Each "box" has one
hoot-n-holler
line.  I would like to make these boxes IP based by connecting the 4
lines to a TDM400 with 4 fxo modules, providing SIP or IAX extensions
for each hoot line and giving my clients a softclient on their desktop.
Will it work?  Is it reliable?  Is it the best way?

Thanks in advance for you Asterisk wisdom on this little problem of
mine.

Matthew Machen
Southern Company Network Support

What is it you're trying to accomplish? 

 Squawk Box---------->fxo----------->*---------->IAX2/SIP clients?

 or
 
 replace the 2 wire solution between the different locations with IAX2/SIP?

 The only thing I'd caution you about hear is as you're going back and
forth between 2 wire and IAX2/SIP along with conferencing/meetme in a
hoot/holler application be real careful that you've worked all the
kinks out with echo cancelation. Some echo thrown back into
conference, as you probably already know, could get real ugly real
quick.


On 4/18/05, Machen, Matthew T. <MTMACHEN@southernco.com>
wrote:
> Hello wonderful asterisk users list.
> 
> I have some energy traders that are currently using 2 wire
> hoot-n-hollers (squawk box, always open direct line) to different
> trading floors throughout the country.  Each "box" has one
hoot-n-holler
> line.  I would like to make these boxes IP based by connecting the 4
> lines to a TDM400 with 4 fxo modules, providing SIP or IAX extensions
> for each hoot line and giving my clients a softclient on their desktop.
> Will it work?  Is it reliable?  Is it the best way?
> 
> Thanks in advance for you Asterisk wisdom on this little problem of
> mine.
> 
> Matthew Machen
> Southern Company Network Support
> 
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> Hello wonderful asterisk users list.  
> 
> I have some energy traders that are currently using 2 wire
> hoot-n-hollers (squawk box, always open direct line) to different
> trading floors throughout the country.  Each "box" has one
hoot-n-holler
> line.  I would like to make these boxes IP based by connecting the 4
> lines to a TDM400 with 4 fxo modules, providing SIP or IAX extensions
> for each hoot line and giving my clients a softclient on their desktop.
> Will it work?  Is it reliable?  Is it the best way?
 
The probability of making that work with a TDM card is rather low.

The primary reason is the TDM card (and drivers) are oriented around
ringing come in, some action performed (eg, dialplan), and aswering
the call. Hoot-n-holler circuits don't have those same functions.

In most cases that I'm familiar with, the actual circuit used for
these is four-wire (not 2-wire) and the TDM does not have a four-wire
interface.

Could someone modify the drivers to do that? High probability, but 
that isn't going to be an easy task for the uninitiated.

>> Hello wonderful asterisk users list.
>>
>> I have some energy traders that are currently using 2 wire
>> hoot-n-hollers (squawk box, always open direct line) to different
>> trading floors throughout the country.  Each "box" has one 
>> hoot-n-holler
>> line.  I would like to make these boxes IP based by connecting the 4
>> lines to a TDM400 with 4 fxo modules, providing SIP or IAX extensions
>> for each hoot line and giving my clients a softclient on their 
>> desktop.
>> Will it work?  Is it reliable?  Is it the best way?
>
> The probability of making that work with a TDM card is rather low.
>
> The primary reason is the TDM card (and drivers) are oriented around
> ringing come in, some action performed (eg, dialplan), and aswering
> the call. Hoot-n-holler circuits don't have those same functions.
>
> In most cases that I'm familiar with, the actual circuit used for
> these is four-wire (not 2-wire) and the TDM does not have a four-wire
> interface.
>
> Could someone modify the drivers to do that? High probability, but
> that isn't going to be an easy task for the uninitiated.
Asterisk can make this happen, but you might have to ditch your current 
equipment.  I'm assuming, though, that the reason you want to do this 
is to eliminate the costs of the lines.  I think you'll really need to 
justify the cost of using bandwidth instead, buying the asterisk boxes, 
setting up QoS, time to configure.  Asterisk is not a trivial thing to 
set up, and I would only do it if it's going to do something more than 
just this one function.  The idea behind asterisk is that it does many 
things any connects many things.

We do something similar with Polycom SIP phones, but it is not always 
on.  PSTN phone networks have gotten to the point where they are 
(supposedly) reliable to five nines (99.999%).  IP networks are NOT 
there, so you'd probably have to do things to make sure that your "IP 
hoot-n-holler" setup is self-healing in case your connections do ever 
go down.  If you use your IP connections for other traffic, there will 
also be QoS issues to deal with.  You'll probably have to make sure 
your voice traffic is getting priority over everything else, or there 
will likely be audio quality issues.