KVM Switch FAQs

KVM Switch Direct has been supplying KVM solutions since 1985 and is an authorised distributor for Adder Technology, Austin Hughes and ATEN. Here are answers to the questions we're asked most often about KVM switches.

What is a KVM Switch and why might I need one?

A KVM (keyboard, video and mouse) switch lets you control two or more computers from a single keyboard, monitor and mouse. You might need one if you work across several computers at one desk, such as a work laptop and a home PC, or manage multiple servers in a rack without wanting a screen and keyboard for each. It saves space, cost and the hassle of swapping cables.

Can a KVM switch support dual, triple or quad monitors?

Yes. Multi-monitor KVM switches, known as dual, triple or quad view, switch two, three or four screens together. Each computer connects to the switch with one video cable per monitor plus a USB cable. Browse our dual view, triple view and quad view KVM switches. Some KVM switches can also be linked together to achieve the same result.

What's the difference between a KVM switch and an HDMI switch?

An HDMI switch switches video and sometimes but not always, audio. An HDMI KVM Switch allows you to control computers with HDMI Video ports using your keyboard, monitor and mouse. With a KVM Switch each computer needs a USB cable to the switch as well as an HDMI cable.

Will my wireless keyboard and mouse work with a KVM switch?

Possibly not and you should seek advice. There are three things to be aware of:

1. Power. Passive, mainly cable type KVM Switches typically will not provide enough power through the console ports to power the transmitter (wireless dongle).
2. Emulation. KVM switches have separate Keyboard and mouse ports which are specific and not interchangeable. The Keyboard port is emulated to enable the use of 'Hotkey' switching and maintenance, whilst the mouse port is typically not emulated and in some cases is 'transparent'. Wireless Desktops tend to share a wireless dongle. This is a problem because if you plug it into the keyboard port the mouse will not work and if you plug it into the mouse port you will not be able to switch using 'Hotkeys'. Some switches have a USB hub or "transparent" port that works with wireless receivers, usually without hotkey support.
3. Bluetooth. Bluetooth keyboards and mice pair directly with a computer and bypass the switch altogether.

Does a KVM switch support 4K / high refresh rates?

Yes, increasingly there are models that support up to 8K but you should probably stick to the leading brands as there have been many reports of problems with low-cost unbranded switches sold online. Here are some 4K KVM Switches and 8K KVM Switches. For 4K at 60Hz, look for HDMI 2.0 or DisplayPort 1.2 support or later. For high-refresh gaming monitors (120Hz and above), check the switch's stated maximum refresh rate at your resolution, as many are limited.

How do I switch between computers: buttons, hotkeys or on-screen display (OSD)?

If you are only controlling a few computers, it may be worth getting a desktop switch that has push buttons as it is the quickest and most intuitive method. Almost all KVM Switches support 'hotkey' switching and this may be the best method if you have more than six computers to switch. OSD (On Screen Display) is not typically an option on desktop switches and is usually unnecessary on a small desktop setup.

Can I use a KVM switch with a Mac and a PC together?

The short answer is yes, KVM switches switch the computer console inputs and are untroubled by the operating systems on the connected computers. They do however care about the keyboards connected to them. Keyboards on KVM switches are emulated and have to be 'understood' by the KVM Switch. All KVM switches support the popular PC keyboards, some support Mac, others partially support Mac i.e. all the common keys and others do not support Mac keyboards at all. Check compatibility first.

Do KVM switches need drivers or software?

Standard KVM switches are plug-and-play and need no drivers or software. The connected computers simply see an ordinary keyboard, mouse and monitor. The exceptions are optional utilities on some models, such as firmware updaters or software for mouse-based switching, and KVM over IP switches, which you access through a web browser or viewer application.

How many ports do I need, and can KVM switches be cascaded?

KVM Switches generally have either 2, 4, 6, 8, 16 or 32 ports and rack mounted switches can generally be cascaded to support hundreds of computers. The choice is generally determined by the number of computers you have, however bear in mind that a 16 port KVM Switch is sometimes little more cost than an 8 port and it may be a better option for redundancy and future expansion.

What is a secure KVM switch, and when is one required?

A Secure KVM switch lets one user operate computers on networks of different security levels, such as classified and unclassified systems, from a single keyboard, monitor and mouse, while preventing any data passing between them. It does this through one-way data paths, isolated USB, video and audio channels, no shared memory, keyboard buffer purging on switching, and tamper-evident enclosures. Secure KVMs are required in government, defence and other high-security environments, and are typically certified under Common Criteria to the NIAP Protection Profile for Peripheral Sharing Devices. A standard KVM switch should never be used in place of one. Due to the nature of these switches they are normally manufactured to order and shipped directly from the manufacturer so you will not see many offered online. Please email your initial enquiry to sales@kvmswitchdirect.co.uk and we can lay out the available options.

Why is there a delay or blank screen when I switch?

Longer delays in switching happen when the KVM Switch does not save or emulate EDID information (monitor identification data). HDMI and DisplayPort switching always involves a short handshake delay, and HDCP-protected content can add to it. Blank screens however can occur for a number of reasons including faulty or inadequate cabling, or trying to connect devices with resolutions, aspect ratios or refresh rates outside the stated capability of the switch.

Do I need a USB cable as well as a video cable?

Yes, in most cases. Video cables such as HDMI, DisplayPort, DVI and VGA carry only the picture (HDMI and DisplayPort can also carry audio), so each computer also needs a USB cable to the KVM switch for the keyboard and mouse to work. Without it, you'll be able to switch the screen but not control the computer. Each computer therefore typically needs one video cable per monitor, plus one USB cable, plus an audio cable if you want to switch speakers or a headset. Many manufacturers offer KVM cable sets that combine video and USB in a single cable, which keeps things tidy and these cable sets are often included with the switch. See our Manufacturer Specific Cables. Some USB-C KVM switches use a single USB-C cable to carry video, USB and sometimes power. Older switches with PS/2 ports use PS/2 keyboard and mouse cables instead of USB. 

What's the difference between a desktop and a rackmount KVM switch?

A desktop KVM switch is a compact unit for controlling a few computers at a single desk, while a rackmount KVM switch fits in a 19-inch server cabinet and is designed to manage many servers from one console.

Desktop switches usually have 2 to 4 ports, sometimes 8, with front-panel buttons for quick switching. They often support high resolutions, multiple monitors, audio and USB peripherals, making them ideal for offices, trading desks and home workstations. Browse our desktop KVM switches.

Rackmount switches usually take up 1U or 2U of rack space and have 8 to 64 ports. They add features suited to server rooms, such as on-screen display (OSD) menus for naming and selecting servers, cascading to control hundreds of servers, and connection via compact interface modules (CIMs) over Cat5/Cat6 cable. Some models also offer additional user consoles or remote access over IP. They're commonly paired with a rack console drawer for a complete keyboard, screen and mouse in 1U. Browse our rackmount KVM switches.

Some desktop switches can also be fitted in a rack using a rack mounting kit.

Can I use a KVM switch with a laptop, USB-C or a docking station?

Yes. A laptop connects to a KVM switch in the same way as a desktop computer: a cable from its video output and a USB cable to the switch.

If your laptop only has USB-C ports, you have two options. You can use a USB-C KVM switch, where a single cable carries video, keyboard and mouse, and on some models charges the laptop too. Alternatively, you can use a USB-C to HDMI or DisplayPort adapter with a standard KVM switch. Either way, check that your laptop's USB-C port supports video output (DisplayPort Alt Mode or Thunderbolt), as not all USB-C ports do.

You can also connect a docking station by running the dock's video outputs and a USB connection from the dock to the switch. This generally works well, but docks that use DisplayLink technology rely on drivers and compressed video, which can cause compatibility problems, so ask us before buying.

For dual or triple monitor setups, check how many external displays your laptop supports. Some, including several MacBook models, are limited to one or two. Laptops can also rearrange open windows when you switch away. A switch with full EDID emulation, or one of our EDID management adapters, helps prevent this.

Can't find your answer? Call our team on 01372 451345 or email sales@kvmswitchdirect.co.uk, and we'll help you choose the right switch.