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From: laser-lovers@uw-beaver
Newsgroups: fa.laser-lovers
Subject: Re: a Slur on Symbolics
Message-ID: <627@uw-beaver>
Date: Mon, 28-Jan-85 20:39:25 EST
Article-I.D.: uw-beave.627
Posted: Mon Jan 28 20:39:25 1985
Date-Received: Wed, 30-Jan-85 05:26:52 EST
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Organization: U of Washington Computer Science
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From: Brian Reid <reid@Glacier>

Peter Gross from the High Altitude Observatory (I think that's what
"hao" stands for) sent the following comment that I can't allow to go
unflamed.

    From: udenva!hao!pag@lbl-csam.arpa (Peter Gross)

    I'm not familiar with the Canon LBP-CX engine, but I can give you
    a {possible} warning about it.  We have three Symbolics lasers
    based on the LBP-10 engine from Canon.  For the same reason (high
    costs) as well as difficulty in delivery (they're in Ca., we're
    in NC) we attempted to find another supplier for the Canon LBP-10
    toner and concentrate.  Turns out stock Canon supplies will NOT
    work.  Symbolics deliberately changed the POLARITY on their toner
    fluid such that you MUST buy your supplies from them.  I doubt
    Imagen did something similar, but you never know.

    Personaly I'd never buy Symbolics again, but once we had two in
    house, we had no choice but to get our third from them because of
    maintenance agreements. Just thought I'd give you a small word of
    caution.  Make sure Imagen hasn't pulled some sort of similar
    trick to make you dependent upon them.

I completely refuse to believe you. For one thing, Symbolics does
not have the in-house technical expertise to change the imaging
polarity on a marking engine. They just buy LBP-10's from Canon
and stick a Symbolics controller on them. For another thing, I'm
sure that Symbolics has better things to do than sell toner. They
are a computer company.

The LBP-10 has reversed polarity from an ordinary copier.
That means you can't use ordinary copier supplies in it. This has
nothing to do with anything Symbolics did, or could do, or that Imagen
could do. That's just the way that the LBP-10 works. What "reversed
polarity" means is as follows. In an ordinary copier you put a piece of
paper in, and the copier shines a light at the paper. Anywhere the
paper is white, light is reflected onto the drum. Anywhere the paper is
black, light is not reflected onto the drum. It is then the drum's job
to make the copy black in places where light did not hit it and white
in places where light did hit it. I believe that this is called
"positive imaging"; I am certain that it is also called "write-white".

It turns out to be more convenient to make a laser printer work the
other way--anyplace you want it to be black, you shine a light at it,
and anyplace you do not want it to be black, you do not shine a light
at it. I believe that this is called "negative imaging"; it is also
called "write-black".

My recollection is that the LBP-10 is a write-black system, which is
the opposite polarity from a usual copier. This is why you can't use
ordinary copier supplies in it. It is for precisely this same reason
that you can't use Canon Personal Copier supplies in a Canon LBP-CX.
--
	Brian Reid	decwrl!glacier!reid
	Stanford	reid@SU-Glacier.ARPA