[Asterisk-Users] OT (maybe?) : TI - PRI Question

[Michael Loftis]

--On Thursday, September 30, 2004 17:49 -0500 Steve Maroney 
<steve at stevenet.net> wrote:

>
>
> Hey guys,
>
> Im new to the telecom industry and I am having a hard time understanding
> the differences between a voice T1 and a PRI line ? I was taught by a
> friend that I met on this list that a voice T1 provides all 24
> channels for voice and/or data and uses inband signalling. PRI uses 1
> channel for signalling and leaves the other 23 channels for either voice
> or data.
>
> This makes sense but how else does T1 compare/contrast to a PRI ?

ISDN PRI does travel on a T1 circuit.  The 'T1' your friend is talking 
about is called DSS or 'E&M' T1 service.  It's exactly the same as taking 
24 analog phone lines, and putting them on a digital transport.  You may 
also get some inband signalling options for DID information, but often 
times this isn't offered.  DSS service is usually only slightly cheaper 
than an ISDN PRI, and you don't get any control over CID information with 
DSS.  With PRI you can set the outgoing CID information (important if you 
don't want your non-trunk DIDs exposed)

> Doesn't a T1 carry the PRI signal(such as UDP over IP) ?
> Does the T1 cards from digium support both voice T1's and PRI lines ?
> What benefits and features does a PRI line have over a T1 and vice versa ?
> I learned a little about the use of DIDs with PRI. Does DIDs apply to
> voice T1s ?

AFAIK The Digium cards support basically every single type of common T1 
delivery, including 'feature group' D in-band and a few other in-band 
signals.  Lots of options.


> HELP !
>
> A link to a good article will be appreaciated as well as someones
> explanation.

Your best bet, if you're provisioning an office is to go with ISDN PRI, it 
will do what you want.