[Asterisk-Dev] Channel bank w/ bri card and Zaptel

[Steven Critchfield]

On Thu, 2003-04-03 at 19:36, George Bean wrote:
>  > 4:1 TDM is where 4 BRI lines share a DS0 for the D channel
> > 
> > 3DS0 BRITE is where the ISDN BRI uses 3 DS0 channels and the D is on a
> > DS0 of it's own.
> > 
> > Don't know more, but this hopefully will help if you want to shake
> down
> > some documentation more than what this says. It would be nice if both
> > kinds of muxing are available.
> > 
> > Out of curiousity, wouldn't this be the same type of information as is
> > in the D channel of a PRI, and therefore maybe mostly implemented
> > already in libpri?
> > 
> The BRITE configuration is much more prevalent than the 4:1 TDM version
> among several manufacturers of ISDN extension equipment. The D channel
> information contained in the third DSO of the BRITE grouping is 1/23 of
> the PRI signaling channel. The 4:1 TDM signaling DSO contains 4/23 of a
> PRI signaling channel. It's conceivable that the libpri could be
> modified to handle the BRITE/4:1 configuration. This would entail adding
> code to interleave D channel information from the dedicated DS0's on the
> T1 and a configuration line to group DS0's and designate DS0's carrying
> D channel information. Creating a BRITE/4:1 version of libpri would
> definitely provide * users with much needed options for connecting ISDN
> desksets as well as equipment such as video conferencing systems and 56K
> modem terminations.

I'll just say, I don't know how prevelant any kind of service here would
be. I know the BRI card for the ADIT 600 supports both. I'd assume the
same would be true with the Adtran unit since they seem to be fairly
comparable.

As for your math, it is slightly wrong. PRI is 1 64K D channel for 23 B
channels. BRITE places the normally 16K D channel for 2 B channels on a
64K link. If you want to compare it, BRITE is 2/23rds of a PRI. The 4:1
puts 4 D channels on a single 64K channel. The 4:1 uses one 64K channel
for 8 B channels, or 8/23rds of a PRI. This gets you 4 BRI lines in 9
DS0 channels, or 8 BRI lines in 18 DS0s and have a few DS0s left over
for analog.


-- 
Steven Critchfield <critch at basesys.com>