This is good news. I'd rank it up there with 2400 support :)
> I would *not* encourage anyone to use it in the 23B+D and
> 24B format with 2 PRIs as on a PM-3. However, you can add redundancy by
> using it in 23B+Primnary-D and 23B+Backup-D format.
I haven't seen this offered by the telcos or other hardware vendors, and I
can't imagine a scenario where you'd lose only some channels of a T1, so the
primary D would be damaged. Now, if you were passing massive amounts of
packet-switched data, then this might make sense...
> But using it to gain a B channel with the increased risk of problems by
> relying on a single D channel really isn't worth it. (though I'm sure
> some people will do it anyway).
There is no bandwidth problem in relying on a single D channel for 47 B's
when the D is only used for call signalling (no packet-switched data).
You _do_ lose the redundancy, so if the first PRI goes down, both are lost, but
in some areas the tariffs for PRI over T1 is high enough that getting a free
channel (Often a substantial 'savings') is worth the small risk.
The only time I ever lost a T1 for long was when a backhoe took out a rather
important Ameritech fiber run...