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Re: Note from a satisfied customer
W. Curtiss Priest wrote:
> One fine point. It may sound picky, but all modem/ISDN transmissions
> are analog. This phrase of using analog versus digital is simply
> ISDN is simply another form of analog transmission.
> That you cannot hook an analog telephone to the line (as is) simply
> means the analog transmission is different, not digital.
> Let me explain it this way. If we have a series of 0 and 1 bits,
> and tried to send it "digitally" we would be required to have
> a wave that looks like:
> At each "step" from 0 to 1 we have a transition of a voltage or phase
> angle or whatever that makes a transition in zero time. This is a
> true digital step function. But if you check your communications
> handbook you find it takes infinite bandwidth to send a step
> function in zero time.
> W. Curtiss Priest, Director, CITS
> Center for Information, Technology & Society
> 466 Pleasant St., Melrose, MA 02176
> Voice: 617-662-4044 BMSLIB@MITVMA.MIT.EDU
> Fax: 617-662-6882 WWW: gopher://gopher.eff.org:70/11/Groups/CITS
With all due respect, although your explanation of the analog nature of
"digital" transmission is technically correct, it simply confuses an
already confused issue. It is like explaining that the molecules of a
solid are really moving, since the substance is not at 0 degrees K.
True, but so what....if you get hit on the head with the solid, it's
There are generally accepted definitions within the industry of the
meaning and significance of "analog" and "digital" signals and
transmission, and the local loop of a POTS line is the realistic
extent of where true "analog" signals will be found in the modern
telecommuniations plant. All else is "digital" in the sense that
information is encoded into discrete signal domains which may be time
and/or frequency multiplexed with other encoded signals for