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Re: Note from a satisfied customer
- To: ISDN Discussion list <isdn@ESSENTIAL.ORG>
- Subject: Re: Note from a satisfied customer
- From: "W. Curtiss Priest" <BMSLIB@MITVMA.MIT.EDU>
- Date: Mon, 18 Mar 96 16:03:02 EST
- In-Reply-To: Your message of Sun, 17 Mar 1996 19:44:06 -0500 (EST)
One fine point. It may sound picky, but all modem/ISDN transmissions
are analog. This phrase of using analog versus digital is simply
incorrect.
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.
OK?
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