KVM switches

Discussion in 'NZ Computing' started by SCCC, Jul 5, 2005.

  1. SCCC

    SCCC Guest

    I want to use a 4 port electronic KVM switch to switch only the VGA
    signals. A number of models have pushbutton switches fitted on the front
    panel to select which input is required.

    The keyboard and mouse connectors will not be used in this instance as
    we want them to remain connected to the primary computer. The use in
    this case is to act as a multi input switch for VGA video routed to a
    projector.

    If the KVM switch has its own power supply, is there any reason why it
    shouldn't work properly without connection to keyboard and mouse ports
    on any computers? Some units derive their power from the keyboard port,
    which is why I specified that it have a separate power supply.

    Models by Novaview and others appear to meet these specs. There is
    little need for the autoscan features most of these devices have when no
    keyboard or mouse will ever be connected.
    SCCC, Jul 5, 2005
    #1
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  2. SCCC

    SNOman Guest

    SCCC wrote:
    > I want to use a 4 port electronic KVM switch to switch only the VGA
    > signals. A number of models have pushbutton switches fitted on the front
    > panel to select which input is required.
    >
    > The keyboard and mouse connectors will not be used in this instance as
    > we want them to remain connected to the primary computer. The use in
    > this case is to act as a multi input switch for VGA video routed to a
    > projector.
    >
    > If the KVM switch has its own power supply, is there any reason why it
    > shouldn't work properly without connection to keyboard and mouse ports
    > on any computers? Some units derive their power from the keyboard port,
    > which is why I specified that it have a separate power supply.
    >
    > Models by Novaview and others appear to meet these specs. There is
    > little need for the autoscan features most of these devices have when no
    > keyboard or mouse will ever be connected.


    I'm in the process of trying to do exactly the same thing at this moment
    for two notebooks to a projector. Have found that kvm type switch will
    not work for this. You need a good old fashioned manual 15 pin vga
    switchbox ala
    http://www.sicom.co.nz/xurl/function/viewprd/prd_id/73115/2-way-vga-monitor-switch.html
    SNOman, Jul 5, 2005
    #2
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  3. SCCC

    Harry Guest

    SCCC wrote:

    > I want to use a 4 port electronic KVM switch to switch only the VGA
    > signals. A number of models have pushbutton switches fitted on the front
    > panel to select which input is required.
    >
    > The keyboard and mouse connectors will not be used in this instance as
    > we want them to remain connected to the primary computer. The use in
    > this case is to act as a multi input switch for VGA video routed to a
    > projector.
    >
    > If the KVM switch has its own power supply, is there any reason why it
    > shouldn't work properly without connection to keyboard and mouse ports
    > on any computers? Some units derive their power from the keyboard port,
    > which is why I specified that it have a separate power supply.
    >
    > Models by Novaview and others appear to meet these specs. There is
    > little need for the autoscan features most of these devices have when no
    > keyboard or mouse will ever be connected.


    You could create a special keyboard cable which just has the power supply.
    Or you could even connect to USB power supply with a special cable.
    You would have to make the cable yourself.

    You can also jumper the one keyboard power supply to multiple inputs
    using diodes if necessary (depends on model of KVM).
    Harry, Jul 5, 2005
    #3
  4. SCCC

    Ewen McNeill Guest

    In article <vYkye.12857$>,
    SCCC <> wrote:
    >I want to use a 4 port electronic KVM switch to switch only the VGA
    >signals. [....] If the KVM switch has its own power supply, is there
    >any reason why it shouldn't work properly without connection to
    >keyboard and mouse ports on any computers?


    I would expect it to work like that providing there was a separate power
    source for the KVM switch. The Novaview KVM switches I have will power
    up if either (a) there is at least one machine with a keyboard port
    plugged in _or_ (b) the supplied power supply is plugged in. And they'll
    definitely let you switch to a port which doesn't have the keyboard signal
    connected/active (the port button will not show as green, but you can
    still select it and see the video signal).

    If you have no keyboard lines connected them obviously "keyboard switching"
    and the autoscan features won't work, but switching through the push
    buttons on the front should still work.

    As someone else pointed out you could also use one of the manual
    KVM switches (with a bit rotary knob) as they require no power. But
    beware that the manual ones have a lot less video bandwidth than electronic
    KVM switches like the NovaView so you'll get ghosting, etc, if you
    use a high screen resolution or refresh speed.

    Ewen
    Ewen McNeill, Jul 5, 2005
    #4
  5. SCCC

    SCCC Guest

    Yes I have noticed that the Novaviews and the like offer 2048x15..
    resolution support.
    The rotary ones are not available in more than 2 ports commonly. Plus they
    do not use any special components internally, they have a two position
    switch with a huge number of poles and just plain wires running from the
    terminals to each pole. Not using the proper kind of wires would generate
    all sorts of problems with connected stuff and the switch is probably just a
    plain old one. VGA uses 75 ohm coax so if the wiring and switch do not match
    there are bound to be problems.

    The other issue I want to resolve if possible is the loss of sync signals
    when switching on a manual switch unit. This causes the picture to blink a
    lot and connected projectors can lose custom settings as they reset
    themselves to a default configuration.

    I wondered what the autoscan feature was, obviously I don't want any feature
    that might cause the switch to switch displays by itself.

    I see Novaview are doing DVI now. But as our application requires signal
    boosting as well I can't see how we could go to DVI unless signal boosting
    for long cables becomes available.


    "Ewen McNeill" <> wrote in message
    news:dactck$737$...
    > In article <vYkye.12857$>,
    > SCCC <> wrote:
    >>I want to use a 4 port electronic KVM switch to switch only the VGA
    >>signals. [....] If the KVM switch has its own power supply, is there
    >>any reason why it shouldn't work properly without connection to
    >>keyboard and mouse ports on any computers?

    >
    > I would expect it to work like that providing there was a separate power
    > source for the KVM switch. The Novaview KVM switches I have will power
    > up if either (a) there is at least one machine with a keyboard port
    > plugged in _or_ (b) the supplied power supply is plugged in. And they'll
    > definitely let you switch to a port which doesn't have the keyboard signal
    > connected/active (the port button will not show as green, but you can
    > still select it and see the video signal).
    >
    > If you have no keyboard lines connected them obviously "keyboard
    > switching"
    > and the autoscan features won't work, but switching through the push
    > buttons on the front should still work.
    >
    > As someone else pointed out you could also use one of the manual
    > KVM switches (with a bit rotary knob) as they require no power. But
    > beware that the manual ones have a lot less video bandwidth than
    > electronic
    > KVM switches like the NovaView so you'll get ghosting, etc, if you
    > use a high screen resolution or refresh speed.
    >
    > Ewen
    SCCC, Jul 5, 2005
    #5
  6. SCCC

    Ewen McNeill Guest

    In article <dad1pa$619$>, SCCC <> wrote:
    >Yes I have noticed that the Novaviews and the like offer 2048x15..
    >resolution support.


    FWIW, about all that means is that the cables will be the limiting factor
    rather than the KVM switch itself. Ie, with very short, well shielded
    cables you might be able to do that. With longer cables, or lower quality
    cables, expect the usable resolution to be lower. That said, I've run
    800x600 @ 60Hz over a 10M cable through one of my NovaViews and it's
    quite usuable; with some other KVM switches I've tried it wasn't really
    readable.

    >The rotary ones are not available in more than 2 ports commonly.


    I've often seen 4 port rotary switches (I even own a couple of them).
    But possibly they're not available any longer since the electronic ones
    have come down in price. (When I got them the rotary 4-port switches
    were about $100 with cheap cables, and the electronic ones were several
    hundred, plus cables.)

    But yes, you're right they're just a multi-pole switch internally, and
    cause all sorts of interesting effects when switching. (It was particularly
    bad with keyboards.)

    >The other issue I want to resolve if possible is the loss of sync signals
    >when switching on a manual switch unit.


    Right. An electronic unit should be much better for that. The monitor
    will resync on the signal change if the video frequency is different, but
    there's not the dramatic discontinuity that happens with a manual switch.
    Hopefully if all the display frequencies are the same/similar you shouldn't
    see enough switching change to disturb a projector, etc.

    >I wondered what the autoscan feature was, obviously I don't want any feature
    >that might cause the switch to switch displays by itself.


    From memory you have to manually enable the auto-scan (by pushing a pair
    of buttons) and what it does is cycle through the "active" (detected
    by keyboard signal) ports in some time cycle. I guess it's intended
    for some sort of monitoring/security environment. I've never used it.
    As I said, it probably won't work for you, but that's probably no loss.

    Anyway hope that's of some help. I'm definitely pleased with my Novaview
    KVM switches, and the ability to cascade them is also handy. Hopefully
    they'll work for your application too.

    Ewen
    Ewen McNeill, Jul 5, 2005
    #6
  7. SCCC

    Bling-Bling Guest

    On Tue, 05 Jul 2005 13:00:08 +1200, SCCC wrote:

    > If the KVM switch has its own power supply, is there any reason why it
    > shouldn't work properly without connection to keyboard and mouse ports
    > on any computers?


    No - no reason at all.

    I have an electronic four-port KVM switch to connect the video output of
    two computers in my server room to one monitor. Only one of those
    computers has the keyboard and mouse connected to the KVM switch - and
    that was purely because I didn't want a wallwart sticking out where the
    servers were plugged in to the power.


    Bling Bling

    --
    IBM: "Linux is not just another operating system. It represents a
    collaboration of the best programmers in the industry coming together to
    create an operating system that works on any hardware platform."
    Bling-Bling, Jul 5, 2005
    #7
  8. SCCC

    SCCC Guest

    Bling-Bling wrote:
    > On Tue, 05 Jul 2005 13:00:08 +1200, SCCC wrote:
    >
    >
    >>If the KVM switch has its own power supply, is there any reason why it
    >>shouldn't work properly without connection to keyboard and mouse ports
    >>on any computers?

    >
    >
    > No - no reason at all.
    >
    > I have an electronic four-port KVM switch to connect the video output of
    > two computers in my server room to one monitor. Only one of those
    > computers has the keyboard and mouse connected to the KVM switch - and
    > that was purely because I didn't want a wallwart sticking out where the
    > servers were plugged in to the power.
    >
    >
    > Bling Bling
    >


    Is there no actual keyboard or mouse plugged into the ports on the KVM?
    SCCC, Jul 6, 2005
    #8
  9. SCCC

    Bling-Bling Guest

    On Wed, 06 Jul 2005 16:49:14 +1200, SCCC wrote:

    >>>If the KVM switch has its own power supply, is there any reason why it
    >>>shouldn't work properly without connection to keyboard and mouse ports
    >>>on any computers?

    >>
    >>
    >> No - no reason at all.
    >>
    >> I have an electronic four-port KVM switch to connect the video output of
    >> two computers in my server room to one monitor. Only one of those
    >> computers has the keyboard and mouse connected to the KVM switch - and
    >> that was purely because I didn't want a wallwart sticking out where the
    >> servers were plugged in to the power.

    >
    > Is there no actual keyboard or mouse plugged into the ports on the KVM?


    Go back and read again what I typed!


    Bling Bling

    --
    The above reply is in response to a person who can be only described as
    blind!
    Bling-Bling, Jul 6, 2005
    #9
  10. SCCC

    SCCC Guest

    "Bling-Bling" <> wrote in message
    news:pan.2005.07.06.11.55.16.494956@TRACKER...
    > On Wed, 06 Jul 2005 16:49:14 +1200, SCCC wrote:
    >
    >>>>If the KVM switch has its own power supply, is there any reason why it
    >>>>shouldn't work properly without connection to keyboard and mouse ports
    >>>>on any computers?
    >>>
    >>>
    >>> No - no reason at all.
    >>>
    >>> I have an electronic four-port KVM switch to connect the video output of
    >>> two computers in my server room to one monitor. Only one of those
    >>> computers has the keyboard and mouse connected to the KVM switch - and
    >>> that was purely because I didn't want a wallwart sticking out where the
    >>> servers were plugged in to the power.

    >>
    >> Is there no actual keyboard or mouse plugged into the ports on the KVM?

    >
    > Go back and read again what I typed!


    It would have taken you less time to reply than to write rubbish like that.

    The KVM has both ports for your computer's keyboard and mouse inputs, and
    ports for the actual keyboard and mouse themselves.

    Now, think about that for a minute, and then try answering my question
    again.
    SCCC, Jul 7, 2005
    #10
  11. SCCC

    H.O.G Guest

    On Thu, 7 Jul 2005 14:29:18 +1200, "SCCC" <> spoke these
    fine words:

    >>> Is there no actual keyboard or mouse plugged into the ports on the KVM?

    >>
    >> Go back and read again what I typed!

    >
    >It would have taken you less time to reply than to write rubbish like that.


    Welcome to the world of Bling.


    The answer is that this should work, does work in one of our server
    installations (KVM switch between 3 machines, no keyboard or mouse
    plugged in (it's just for video), and everything works a charm.

    This is with a Nova View 4-port model. YMMV with other models.
    H.O.G, Jul 7, 2005
    #11
  12. SCCC

    SCCC Guest

    Do you have the model with the OSD or without.

    The one with the OSD, which we are trying out at present, puts the port
    number in the middle or corner of the screen.

    If the model without the OSD does not display this number then I would
    prefer the non OSD model.

    "Ewen McNeill" <> wrote in message
    news:dad4hb$8uf$...
    > In article <dad1pa$619$>, SCCC <> wrote:
    >>Yes I have noticed that the Novaviews and the like offer 2048x15..
    >>resolution support.
    SCCC, Jul 13, 2005
    #12
  13. SCCC

    SCCC Guest

    "H.O.G" <> wrote in message
    news:...
    > On Thu, 7 Jul 2005 14:29:18 +1200, "SCCC" <> spoke these
    > fine words:
    >
    >>>> Is there no actual keyboard or mouse plugged into the ports on the KVM?
    >>>
    >>> Go back and read again what I typed!

    >>
    >>It would have taken you less time to reply than to write rubbish like
    >>that.

    >
    > Welcome to the world of Bling.
    >
    >
    > The answer is that this should work, does work in one of our server
    > installations (KVM switch between 3 machines, no keyboard or mouse
    > plugged in (it's just for video), and everything works a charm.
    >
    > This is with a Nova View 4-port model. YMMV with other models.


    If you have a model without the OSD feature, does it display anything on the
    screen when you switch inputs?

    I am trying out one with the OSD, and it puts the port number on the screen,
    which I find annoying.
    SCCC, Jul 13, 2005
    #13
  14. SCCC

    Ewen McNeill Guest

    In article <db2d2v$850$>, SCCC <> wrote:
    >Do you have the model with the OSD or without.


    I've got both non-OSD models and OSD models. To the best of my knowledge
    they work they same except for the on screen display part.

    BTW, I believe there's a configuration option (in the on screen menu)
    to both change the location of the on screen indication of the port number
    and also to disable it completely. The one without OSD doesn' even
    have the option to display the port number, and is a little cheaper,
    so if you have no need for the on screen options it's probably better
    for you.

    Ewen
    Ewen McNeill, Jul 13, 2005
    #14
  15. SCCC

    SCCC Guest

    The OSD model has the option only to change the position but not to disable.

    Our supplier told us the KNV104 was not available and gave use the KNV104D
    for the same price. But as the 104D has the annoying OSD (we are using it
    with a projector and don't want the number flashing up on the screen as it's
    a distraction) and it turned out to be faulty as well I'll get it swapped
    for plain 104.

    So can you confirm that when you press the button on the non OSD model
    nothing appears on the screen at all?


    "Ewen McNeill" <> wrote in message
    news:db2glp$32v$...
    > In article <db2d2v$850$>, SCCC <> wrote:
    >>Do you have the model with the OSD or without.

    >
    > I've got both non-OSD models and OSD models. To the best of my knowledge
    > they work they same except for the on screen display part.
    >
    > BTW, I believe there's a configuration option (in the on screen menu)
    > to both change the location of the on screen indication of the port number
    > and also to disable it completely. The one without OSD doesn' even
    > have the option to display the port number, and is a little cheaper,
    > so if you have no need for the on screen options it's probably better
    > for you.
    >
    > Ewen
    SCCC, Jul 13, 2005
    #15
  16. SCCC

    Ewen McNeill Guest

    In article <db2ibn$lje$>, SCCC <> wrote:
    >The OSD model has the option only to change the position but not to disable.


    Curious. I'll try to remember to double check next time I'm in the office
    where my OSD model is, but I don't recall seeing anything on screen to
    indicate the port, except briefly when switching ports. I've definitely used
    OSD KVMs where it's possible to turn it on/off, and I thought the NovaView
    was one of them. (Alas Rextron's site doesn't seem to have the manuals
    available for download.)

    >So can you confirm that when you press the button on the non OSD model
    >nothing appears on the screen at all?


    Nothing from the KVM appears on the screen with the non-OSD models
    (the screen from the computer connected to that port appears on
    screen though :) ).

    I've just double checked with the KNV104 here, and definitely nothing from
    the KVM switch ever appears on screen; you can keyboard switch it to
    different ports like the OSD model, and do all the other things like the
    OSD model, but the KVM doesn't generate anything on screen.

    Sounds like you want the KNV104 for your task if you can't find an
    option to disable the on-screen watermark.

    Ewen
    Ewen McNeill, Jul 13, 2005
    #16
  17. SCCC

    H.O.G Guest

    On Wed, 13 Jul 2005 18:43:52 +1200, "SCCC" <> spoke these
    fine words:

    >
    >"H.O.G" <> wrote in message
    >news:...
    >> On Thu, 7 Jul 2005 14:29:18 +1200, "SCCC" <> spoke these
    >> fine words:
    >>
    >>>>> Is there no actual keyboard or mouse plugged into the ports on the KVM?
    >>>>
    >>>> Go back and read again what I typed!
    >>>
    >>>It would have taken you less time to reply than to write rubbish like
    >>>that.

    >>
    >> Welcome to the world of Bling.
    >>
    >>
    >> The answer is that this should work, does work in one of our server
    >> installations (KVM switch between 3 machines, no keyboard or mouse
    >> plugged in (it's just for video), and everything works a charm.
    >>
    >> This is with a Nova View 4-port model. YMMV with other models.

    >
    >If you have a model without the OSD feature, does it display anything on the
    >screen when you switch inputs?
    >
    >I am trying out one with the OSD, and it puts the port number on the screen,
    >which I find annoying.
    >

    Yeah, we've got the OSD models throughout, and have never used the OSD
    features... Waste of money.
    H.O.G, Jul 13, 2005
    #17
  18. SCCC

    Enkidu Guest

    H.O.G wrote:
    >
    > Yeah, we've got the OSD models throughout, and have
    > never used the OSD features... Waste of money.
    >

    How do you navigate around your KVMs if you don't use the
    OSD? Surely you don't walk over to the first KVM, punch the
    button for the next KVM and walk over to the next KVm, and
    hit the button for the machine you want, then do it all
    again when you want to change machines? I admit that I had
    shortcuts for the commonly used machines that I used to do
    Ctrl, Ctrl, 1, 4 to get to, for example, butt for lesser
    used machines, Ctrl, Ctrl, Ctrl and navigate the OSD was
    much quicker!

    Cheers,

    Cliff

    --

    Barzoomian the Martian - http://barzoomian.blogspot.com
    Enkidu, Jul 14, 2005
    #18
  19. SCCC

    H.O.G Guest

    On Tue, 05 Jul 2005 13:00:08 +1200, SCCC <> spoke these
    fine words:

    >I want to use a 4 port electronic KVM switch to switch only the VGA
    >signals. A number of models have pushbutton switches fitted on the front
    >panel to select which input is required.
    >
    >The keyboard and mouse connectors will not be used in this instance as
    >we want them to remain connected to the primary computer. The use in
    >this case is to act as a multi input switch for VGA video routed to a
    >projector.
    >
    >If the KVM switch has its own power supply, is there any reason why it
    >shouldn't work properly without connection to keyboard and mouse ports
    >on any computers? Some units derive their power from the keyboard port,
    >which is why I specified that it have a separate power supply.
    >
    >Models by Novaview and others appear to meet these specs. There is
    >little need for the autoscan features most of these devices have when no
    >keyboard or mouse will ever be connected.


    We've only got a single layer of KVM machines, and find it easier to
    just whack one of the buttons on the KVMs, or use the shortcut keys.
    H.O.G, Jul 14, 2005
    #19
  20. SCCC

    SCCC Guest

    Enkidu wrote:
    > H.O.G wrote:
    >
    >>
    >> Yeah, we've got the OSD models throughout, and have

    >
    > > never used the OSD features... Waste of money.
    > >

    > How do you navigate around your KVMs if you don't use the OSD? Surely
    > you don't walk over to the first KVM, punch the button for the next KVM
    > and walk over to the next KVm, and hit the button for the machine you
    > want, then do it all again when you want to change machines? I admit
    > that I had shortcuts for the commonly used machines that I used to do
    > Ctrl, Ctrl, 1, 4 to get to, for example, butt for lesser used machines,
    > Ctrl, Ctrl, Ctrl and navigate the OSD was much quicker!


    In this case, we're only using the switch to select the VGA output. The
    switch sits right next to the projector, and each computer will have its
    own keyboard and mouse - some of them are laptops anyway. Pushing the
    button on the front of the KVM box is actually the most convenient way
    of doing it.
    SCCC, Jul 14, 2005
    #20
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