> first part is correct, but once it is digital at the
> CO, it must stay that way right to (and thru) the ISP.
> ISP's run digital modem banks for 56 k operation with
> PRI lines.
no, no they don't. we, for example, use channelized T1's which of course
stays digital the entire way
and we have an older set of modems hooked into a channelbank for clients
that have older modems or "issues" with the Ascend Max 6096's we run
> two 56 k modems NEVER connect faster than 33.6 k to each other. 56 k
> service is asymetric, server to user can be up to 56 k, but user to
> server cannot be over 33.6 k To operate 56 k, the isp modem is a
> server side 56 k modem (not like the 56 k modem in your pc - but they
> are available in a bri version as well as pri).
bri is an ISDN thing -- modems are analog using POTS
i merely pointed out the analog nature of why 56k modems don't talk 56k to
each other for illustrative purposes, but you are essentially correct in
that 56 is a "receive" only biased speed
> the nasty details, there are two 33.6 k data channels, one channel is
> outbound and the other is inbound (full-duplex). and this is if the
> line is clean enough to support the 33.6 k each way. the additional
> speed from the isp to your pc is created by filling the usable "holes"
> below, between, and above these two channels with MORE bits, which is
> added to the 33.6k channel. this is done with
> multifrequency(multi-tone) modulation, which won't survive a-to-d and
> d-to-a conversions. Which is what happens in a digital phone system,
> the extension is analog, the internal switching is digital and the co
> line is analog again. you've done stripped off the extra speed that
> was stuffed in the holes.
correct
> on the kxtd, there is a way to get 56 k speed. use bri isdn lines!
> the digital internal switching goes out the digital isdn line to the
> isp. no extra conversions in the way. (i have never seen a kxtd
> locally with a bri card, i think australia is the only place they are
> common.)
are you certain that the pots jack on the back of the handset and the a/d
encoding that occurs in the KSU is good enough?
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