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Date:	Mon, 17 Jun 2002 18:12:12 PST7
From:	Michael Rakijas <mrakijas@oco.net >
Reply-To:	scoug-help@scoug.com
To:	scoug-help <scoug-help@scoug.com >
Subject:	SCOUG-Help: Fwd: SCOUG-General: Re: after meeting idea

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** Forwarding message from Michael Rakijas on Sat, 15 Jun 2002 21:15:22 -0700

Although I received the original message from scoug-general, it got bounced on reply. I asked Rollin' to look into it but until that happens, I decided to respond on help hoping to get at least the overlap folks...

** Reply to message from Peter Skye on Fri, 14 Jun 2002
11:17:29 PST7

> J. R. Fox wrote:
> >
> > electronic A/B printer switches that may be on
> > the market now ? I had heard, some years back,
> > that mechanical switches were a very bad idea
> > for laser printers, but that electronic ones would
> > avoid harmful surges.
>
> Foxy,
>
> The mechanical switches should be fine. The cable between the computer
> and printer doesn't carry high voltages and the current flow is _real_
> small, so you shouldn't have any "surges".

I'd be a little careful here. The surges aren't so much a problem as switch
"bounce" and I have heard (admittedly, third or fourth hand) that there can be
some problems here. Mechanical switches do have a nasty habit of changing state
somewhat indeterminately (bouncing between high and low states - hence the term
bounce) and in an unsynchronized way (a few contacts close before others) that
there is the possibility if this being misinterpreted by the printer or computer
as an attempted control signal of some sort, usually garbage. This garbage
usually won't affect say, dot matrix printers but could affect laser printers
that use the bidirectional communications extensively. Using an oscilloscope
with a single trace trigger, you can see this happen with the flick of the
switch which gives some credence to the idea. I find it unlikely that it will
damage anything (although HP for awhile threatened to void warranties of those
who used mechanical switches) but it is entirely believable to me that you could
find intermittent irregularities. I wouldn't be afraid to try it but do expect
that the results could vary. If you want certainty (and network printing is
out), go with the electronic switch. The switches there are debounced to avoid
this problem.

> The signals from the computer to the printer don't change just because
> it's a laser printer; an ink jet printer results in the same signals.
> If a mechanical switch is bad for one then it's bad for both.
>
> Operationally, a network hardware print server still might be the better
> solution. The users doesn't have to flip a switch or (if you have two
> printers on the switch) worry about which printer driver they're
> currently using.
>
> - Electron Pete

-Electric Rocky

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