The one only A/D conversion is the key to get the V.90 (Or any of the
56K modems ) to work correctly. The problem with a lot of business
users is they have a KSU (Mini Telephone Exchange) between them and
the outside phone lines. These units effective are a A/D and D/A
conversion in one box. This kills any hope of V.90. Some PBX's/KSU's
have digital datastreams from the Telco, and the neccesary designing
internally to allow a V.90 to work through them.

There are lots of analog modem racks on the market still, lots still
being installed.
> David Gillett wrote:
>
> > On  2 Dec 98 at 12:52, Jim Meagher wrote:
> >
> > > At your house, the modem is connected to an analog (read that as
> > > voice grade) telephone connection.  At some point, the phone
> > > company will convert that analog signal into a digital signal
> > > (usually the main trunk line).  And -ideally- will convert the
> > > signal back to an analog circuit just before it enters your ISP's
> > > building.  With this perfect scenario, you should be able to
> > > achieve near 56K speeds.
> >
> >   I think one of the stated requirements for 56K is that there NOT be
> > a D-to-A conversion at the ISP's end.  They have to bring a digital
> > T1 or PRI (BRI?) [or better] into a CSU/DSU rather than a bunch of
> > analog lines into modems.
>
> Someone else made a similar comment but I don't believe that it is it
> true.  Yes, it
> would improve the chances of reaching 56K, but I think that the T-1 or
> fractional is
> more a matter of economy/efficiency with the TelCo and not a part of the
> 56K spec.
> The massive number of incoming lines for an ISP almost dictates that it
> has to be digital.
> (Besides, I don't think anyone makes an analog rackmount modem anymore.
> [grin])
>
> The whole reason for developing the V.90 spec, was to allow dissimilar
> modems to
> talk to each other at 56K.  Remember all the problems we saw when the X2
> and Kflex
> modems first came out.  And how we counseled people to wait and see what
> type
> modems your ISP gets.....
Dale Laluk / [log in to unmask]
Design Manager
Lunar Communication Services
P.O. Box 569
Hudson's Hope, B.C. V0C 1V0
250-783-5365

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