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Background

I am looking to switch my keyboard and mouse between a desktop computer and a laptop. The desktop resolution is 2560x1600, which eliminates most (but not all) KVM switches. The monitor has the ability to switch between desktop and laptop. Both computers are plugged into the monitor. The audio is also not an issue for switching.

Problem

All KVM switches I have found come with cables that have physical connectors for audio, video, and USB. In this case, the audio and video connectors are superfluous. I could leave them disconnected, but then there'd be dangling bits of hardware (that a cat or infant could lick or bite). Also, I find the aesthetics of extraneous dangling bits to be displeasing. ;-)

The search results for USB KM switches are overrun by KVM switches, making it difficult to search for this particular hardware device.

Constraints

Hardware solutions only.

Questions

I am wondering:

  • What are such keyboard-mouse (KM) USB switches called?
  • How would you eliminate the superfluous A/V connectors?
  • Optionally, what components would be required to build such a switching device?

I contacted a 2-port USB KVM vendor and they recommended that I use the KVM cables that comes with the switch--as opposed to substituting a regular USB cable.

Update

The device I have in mind would be similar to a USB 2-Way Manual Share Switch. I could use a USB Hub plugged into the Share Switch, but that's two devices when only one should be necessary.

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3 Answers 3

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They are called USB switches, USB Sharing Switches, or USB Peripheral Sharing Switches. The mechanical details of the switch are terribly simple since there are just 4 wires that need to be switched between the two computers for the USB connection (and really only 2 of them where the data passes.. the other two are for power).

If you go the do-it-yourself route, you could probably manage the power for each device separately (red and black wires in the usb wire) with a usb wall charger. And then use a Quad Pole Single Throw switch for the data connections to each device/computer. I haven't tried it myself so YMMV.

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There are a few ways to do this:

  1. USB device switches that simply route all USB connections to whatever PC is selected via the front panel buttons or a wired remote or very rarely a keyboard hotkey. IOGear makes some nice 2-4 port ones, if you are just doing a keyboard and mouse or ESPECIALLY if you use any kind of programmable mechanical keyboard or mouse with extra features "extending" the USB HID specifications you'll probably want one of these. The biggest annoyance is the delay when switching between PC hosts because the OS re-enumerates everything and you get plug/unplug events on the new and previous hosts which can be noisy and generally annoying. $$-$$$ depending on port count

  2. KVM devices, they add video to the USB switching and sometimes audio, handy if you want to share one monitor across multiple machines, annoying if every machine has their own screen already (laptops/All-in-Ones) and unless the KVM does input device emulation and EDID emulation your desktop icons may get screwed up because the machine "loses" the monitor and you have to wait for everything to get recognized after switching. Newer KVMs are often using both types of emulation so switch faster with less headache so if you have suffered with an older one, try upgrading but if you don't need the video or audio you can try the next options. $$-$$$$ depending on port count and extra USB or audio switching that can be independent of the video switching

  3. Cheap KM "port synchronizers" can have some cool features like seamless mouse switching or broadcasting keystrokes to all attached PCs. Some of these don't support the seamless mouse switching but need switched via a hotkey and some don't support broadcasting, so make sure you verify what you are looking at does what you need. $$-$$$ depending on port count

  4. Mid-range KM switchers, usually support seamless switching/glide mouse/mouse roaming or whatever they brand it to make it different from everybody else's version of the same thing. These are sort of a purpose built USB device switcher, some support audio switching as well but not video. $$$-$$$$ depending on port count

  5. Expensive secure KM switches that isolate all ports electrically using opto-electric switches and only accept input from standard HID keyboard and mouse devices not wireless models, and only output audio and don't support input from a microphone. $$$-$$$$$ depending on port count

  • Note that many of the KM devices of any price range don't work well (or AT ALL) with wireless receivers that support many devices to one receiver (like Logitech Unifying) and may only function if each wireless device has a specific paired receiver (and is powered on before the KM powers up).

  • An issue I've seen on KMs and KVMs is that sometimes the hotkeys shadow shortcuts you may want to use or cause other weird behaviors due to intercepting the keystrokes to try and detect the hotkeys.

  • The BIGGEST issue I've found with KMs is that they often fail to recognize and transmit composite keyboard/mouse devices (like mechanical keyboards) or keyboards with a USB hub (some add extra USB ports to the keyboard but some keyboards don't expose the ports but use the additional internal paths to attach the keyboard and a custom HID device for layout programming or backlight control or special shortcut/macros keys). Luckily some keyboard firmwares have an option for more compatible USB and disabling NKRO (N key roll-over, essentially being able to press more than 6 keys at a time and have ALL be recognized, the early HID standards used in BIOS and targeted by KMs for compatibility don't support this and will typically only handle 6 key rollover or less).

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find KVM switches with following spec.

  1. support EDID emulation to all connected systems/laptops of the KVM switch.
  2. video output(s) and audio output can be independently switching to different connected systems of the KVM switch. it called "independent video switching" or video parking/locking,

Normally, those spec. are all supported with DDM-class KVM switches. Found this link that all of the KVM switches listed are DDM-class KVM switches. You just pick what is the video format (VGA, DVI. HDMI or DisplayPort) you want to use for the video switching.

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