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Groups > comp.os.linux.misc > #17031

Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting)

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On 2016-03-17, Kenny McCormack <gazelle@shell.xmission.com> wrote:
> In article <ol5prcxops.ln2@goaway.wombat.san-francisco.ca.us>,
> Keith Keller  <kkeller-usenet@wombat.san-francisco.ca.us> wrote:
> ...
>>> Indeed. You can even fry a PS/2 port or device if you plug or unplug it
>>> while the power is on.
> ...
>>I know this is true in theory, but I have plugged/unplugged PS/2 devices
>>with the power on probably hundreds of times over the past 20 years, and
>>have had one device and one port fry in that time (in unrelated separate
>>incidents).  If you can power down, great.  If not, the risk is low,
>>just be very very sure that you can make alternate arrangements in case
>>you do fry something.
>
> Yeah, I was about to question the, er, if not veracity, shall we say,
> relevance of the previous poster's post.  I'd like to know if he could say
> more about what conditions (actions) would actually cause the noted
> "frying".  My guess is that it would be if you "bounced" the connection -
> that is, sorta made contact, then broke contact, etc - enough times (and in
> just the "right" way).
>
> I say all this because, back in the day, I had a PS/2 KVM at my office
> desk, switching happily between several computers.  Obviously, this was
> hot-swapping a PS/2 mouse and PS/2 keyboard around, and it all worked fine.
> I'm sure this was because the makers of the KVM knew what they were doing
> and knew how to do it safely.  Nowadays, we all have USB KVMs, of course,
> but those were the days...
>
> So, in conclusion, it seems pretty clear that the previous poster's advice
> was much more in the category of "This is what we must tell beginners" than
> in the "This is what is actually true" category.

Switching PS/2 keyboard and mouse with a properly designed KVM is
not necessarily the same thing as physically [un]plugging the
connectors.  The KVM might have active circuitry inside to do the
switching with controlled logic levels.  Even if the KVM was
entirely passive, it could have had Rs, Cs, and maybe Ls to keep
the transient voltages at the instance of switching to reasonable
levels.  The KVM's switch or relay contacts could also be
designed to minimize transients.

While it's not the same thing as a PS/2 port, you can give
yourself a nice little zap with a 9V battery and a _single_
winding of a power or audio transformer (or even a simple choke)
via inductive kick.  You'll get voltages _way_ over 9V.

For another illustration, old-style (1970ish) automotive ignition
systems used inductive kick to transform 12V into a 400V
transient on the _primary_ side of the ignition coil.

-- 
Robert Riches
spamtrap42@jacob21819.net
(Yes, that is one of my email addresses.)

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Thread

Cursor while booting Helge <w4hw4h.hh@gmail.com> - 2016-03-12 02:54 -0800
  Re: Cursor while booting Andreas Kohlbach <march.10.ankman@spamgourmet.net> - 2016-03-12 15:08 -0500
  Re: Cursor while booting w4hw4h.hh@gmail.com - 2016-03-13 00:26 -0800
    Re: Cursor while booting William Unruh <unruh@invalid.ca> - 2016-03-13 16:26 +0000
    Re: Cursor while booting Andreas Kohlbach <march.10.ankman@spamgourmet.net> - 2016-03-13 17:05 -0400
      Re: Cursor while booting w4hw4h.hh@gmail.com - 2016-03-15 02:48 -0700
        Re: Cursor while booting Robert Heller <heller@deepsoft.com> - 2016-03-15 06:25 -0500
          Re: Cursor while booting gazelle@shell.xmission.com (Kenny McCormack) - 2016-03-15 13:32 +0000
            Re: Cursor while booting Reinhardt Behm <rbehm@hushmail.com> - 2016-03-15 22:12 +0800
            Re: Cursor while booting Robert Heller <heller@deepsoft.com> - 2016-03-15 10:48 -0500
              Re: Cursor while booting gazelle@shell.xmission.com (Kenny McCormack) - 2016-03-16 09:20 +0000
              Re: Cursor while booting Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2016-03-16 20:15 +0100
                Re: Cursor while booting Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> - 2016-03-16 16:09 -0700
                Hot-swap-ability of PS/2 devices (Was: Cursor while booting) gazelle@shell.xmission.com (Kenny McCormack) - 2016-03-17 00:31 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Robert Riches <spamtrap42@jacob21819.net> - 2016-03-17 01:10 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) William Unruh <unruh@invalid.ca> - 2016-03-17 05:11 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Robert Heller <heller@deepsoft.com> - 2016-03-16 20:54 -0500
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) William Unruh <unruh@invalid.ca> - 2016-03-17 05:13 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> - 2016-03-17 09:37 -0700
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) William Unruh <unruh@invalid.ca> - 2016-03-17 16:42 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Bobbie Sellers <bliss-sf4ever@dslextreme.com> - 2016-03-17 10:02 -0700
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) "Carlos E.R." <robin_listas@invalid.es> - 2016-03-17 20:11 +0100
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) William Unruh <unruh@invalid.ca> - 2016-03-18 01:55 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Robert Riches <spamtrap42@jacob21819.net> - 2016-03-18 03:21 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) The Natural Philosopher <tnp@invalid.invalid> - 2016-03-18 12:10 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) William Unruh <unruh@invalid.ca> - 2016-03-18 15:33 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) "Carlos E.R." <robin_listas@invalid.es> - 2016-03-18 20:21 +0100
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) William Unruh <unruh@invalid.ca> - 2016-03-17 19:14 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Bobbie Sellers <bliss-sf4ever@dslextreme.com> - 2016-03-17 13:03 -0700
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) William Unruh <unruh@invalid.ca> - 2016-03-18 01:57 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Bobbie Sellers <bliss-sf4ever@dslextreme.com> - 2016-03-17 19:11 -0700
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Robert Heller <heller@deepsoft.com> - 2016-03-17 14:30 -0500
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> - 2016-03-17 14:59 -0700
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Robert Heller <heller@deepsoft.com> - 2016-03-17 18:16 -0500
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Keith Keller <kkeller-usenet@wombat.san-francisco.ca.us> - 2016-03-18 11:07 -0700
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Robert Heller <heller@deepsoft.com> - 2016-03-18 13:49 -0500
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2016-03-18 22:13 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) William Unruh <unruh@invalid.ca> - 2016-03-18 19:55 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Robert Heller <heller@deepsoft.com> - 2016-03-18 15:13 -0500
                Re: Hot-swap-ability of PS/2 devices Andreas Kohlbach <march.10.ankman@spamgourmet.net> - 2016-03-18 14:35 -0400
                Re: Cursor while booting Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2016-03-17 13:31 +0100
                Re: Cursor while booting William Unruh <unruh@invalid.ca> - 2016-03-17 15:04 +0000
                Hot-swap-ability of PS/2 devices (Was: Cursor while booting) gazelle@shell.xmission.com (Kenny McCormack) - 2016-03-17 00:33 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) William Unruh <unruh@invalid.ca> - 2016-03-17 05:09 +0000
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Aragorn <thorongil@telenet.be.invalid> - 2016-03-17 14:15 +0100
                Re: Hot-swap-ability of PS/2 devices (Was: Cursor while booting) Pascal Hambourg <boite-a-spam@plouf.fr.eu.org> - 2016-03-17 15:05 +0100
      Re: Cursor while booting w4hw4h.hh@gmail.com - 2016-03-15 02:49 -0700
        Re: Cursor while booting w4hw4h.hh@gmail.com - 2016-03-15 02:57 -0700
  Re: Cursor while booting Teemu Likonen <tlikonen@iki.fi> - 2016-03-13 11:36 +0200
    Re: Cursor while booting w4hw4h.hh@gmail.com - 2016-03-15 02:47 -0700
      Re: Cursor while booting William Unruh <unruh@invalid.ca> - 2016-03-15 19:45 +0000
    Re: Cursor while booting w4hw4h.hh@gmail.com - 2016-03-15 02:53 -0700
      Re: Cursor while booting The Natural Philosopher <tnp@invalid.invalid> - 2016-03-15 10:02 +0000
  Re: Cursor while booting Chick Tower <c.tower@deadspam.com> - 2016-03-15 16:52 +0000

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