Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!cbmvax!valentin
From: valentin@cbmvax.UUCP (Valentin Pepelea)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Apple SCSI not compatible with standard SCSI?
Message-ID: <8910@cbmvax.UUCP>
Date: 9 Dec 89 11:04:47 GMT
References: <24105@cup.portal.com> <15450001@hpdml93.HP.COM> <593@bmers58.UUCP> <7388@hubcap.clemson.edu>
Reply-To: valentin@cbmvax.UUCP (Valentin Pepelea)
Organization: Commodore Technology, West Chester, PA
Lines: 26

In article <7388@hubcap.clemson.edu> dawill@hubcap.clemson.edu (david williams) writes:
>
>    Since I seem to have started this, I'll answer your question:  Differential
>drive is a technique of sending signals to eliminate noise.  You use two wires
>for each signal.  One wire carries the normal signal, and the other wire carries
>the signal after being inverted.  At the recieving end, you invert the signal
>that was inverted at the transmiter, and add them together.  Any noise on the
>line cancels out (since each line gets the same amount of noise placed on it
>during the traversal of the cable) and you end up with a clean signal.

Not quite. Adding the inversion of the inverted signal to the positive signal
will result in the doubling of the amplitude of the signal. However, the noise
is in no way eliminated. It too in fact increseas in magnitude, but does not
double because it is random by nature. That means that some times you get
spikes which are as high as double in usual magnitude, and sometimes you get
lucky ang get a cancel out.

Visualise this as adding two sinusoidal waves of different magnitude together.
Do they cancel each other out? What is the magnitude of the resultant wave?

Valentin
-- 
The Goddess of democracy? "The tyrants     Name:    Valentin Pepelea
may distroy a statue,  but they cannot     Phone:   (215) 431-9327
kill a god."                               UseNet:  cbmvax!valentin@uunet.uu.net
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