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What is a KVM switch?

This device improves productivity, saves space, and money by allowing you to use multiple computers with one set of keyboard, monitor, and mouse. The exclusive feature offers IT administrators centralized real-time updating and maintenance.

You've just set up your new home office, or have begun work at a new company. As part of your job, you need to use two, sometimes three, computers at your work station. However, setting up three monitors, three keyboards, and three mice is making your desk far too crowded. Plus, there’s the additional hassle of moving around to use each computer. Or perhaps you’re working in a data center with servers in racks. You need to switch among hundreds, perhaps thousands, of servers in rack cabinets. How would you even accomplish this? What if there were a device that could allow you to quickly and easily access two, three, or more computers with just a single monitor, keyboard, and mouse? There is, and it’s called a KVM switch.

KVM 101

KVM stands for “Keyboard, Video (monitor), Mouse.” The main function of a KVM switch is to control, switch between, and manage multiple PCs or servers via a single keyboard, monitor and mouse (also referred to as the ‘console’).

At its most basic, a KVM switch is a hardware device, usually box-like, that connects one set of keyboard, monitor, and mouse to two or more PCs. The PCs are connected to the switch, and the switch is connected to the keyboard, monitor, and mouse.

Fig. 1 By using a KVM switch, a user can access multiple PCs through a single keyboard, video (monitor), and mouse setup.

To switch between the different computers or servers, a user can press a button on the KVM switch, press a hotkey on their keyboard, click on their mouse wheel, or use an on-screen display program. Regardless of which method one chooses, the idea is that you can quickly and easily switch between different computers while using the same keyboard, mouse, and monitor setup.

KVMs use hardware and firmware to ensure switching is smooth, and that your keyboard, monitor, and mouse will work with each computer right away.

Fig. 2 Hotkeys, pushbuttons and OSD are three kinds of port selection methods used with KVM switches.

The benefits of using a KVM switch

Usually if you need to control multiple PCs or servers then you need to purchase several sets of keyboard, mice, and monitors. Perhaps your desk is big enough for 2 or even 4 computers, each with its own monitor, keyboard, and mouse. But what if you need to control 6 computers, or 8, or even tens of computers? Or in a server room application, having a console for each server would be extremely impractical because of how much rack space it would take up. This is not the most effective setup since it is space-consuming. What’s more, keeping a row of large monitors with keyboards and mice at one desk or in a server rack can create clutter and take up valuable space. Thus the KVM switch was "born" from the demands of saving space, costs, and increasing efficiency.

Thus, the key benefits of employing a KVM switch are:

Multiple computer / server control: Users can have quick, easy access to 2, or even much more, PCs or servers from their keyboard, monitor, and mouse setup.
Reducing clutter: Cutting down on the number of keyboards, monitors, and mice needed frees up desk space.
Cost saving: Not needing to invest in extra computer equipment helps save you money.
Space saving: Keep your desk clear, and save much-needed rack space in a server room.
Peripheral support: Some KVM switches support USB peripherals, for example, eliminating the need for separate USB hubs.

As the cost of computers goes down, many users can afford a second or even multiple PCs. As a result, KVM switches are becoming popular with consumers who want to add an extra PC or 2 but don’t want to invest in more sets of keyboards, monitors, and mice. By adopting a desktop KVM switch, a user also gets a neater, more comfortable workspace. Whereas in a server room, KVMs allow for greater efficiency and manageability.

How exactly does a KVM switch work?

When a typical PC is starting up, the operating system will automatically try to detect the incoming signals from the keyboard, mouse, and monitor. After confirmation of connectivity, the monitor then displays the start up page. As a result, the start-up operations of a single PC (CPU/Server) are intricately involved with that of its keyboard, mouse, and monitor. A KVM allows for switching with the correct signals every time through the use of signal emulation technology. (signal emulation technology)

Since the main function of a KVM switch is to use only one set of keyboard, monitor and mouse to start multiple PCs, it is important that the KVM switch ensures the emulated keyboard and mouse signals reach each PC and that during switching there is no effect on the PC’s CPU operations.

A KVM switch must also provide stable video resolution, support multiple computer platforms and operating systems, and be able to interface with many different brands of keyboards, mice, and monitors. Each KVM switch can only support a maximum number of PC connections, i.e. the total number of ports. A single KVM switch can provide as few as two ports, while a multiple KVM switch installation with possible expansion capability reaching up to thousands of ports.

KVM switches: for desktops and server rooms

Different KVM switches can connect to different amounts of computers. It all depends on the number of ports a KVM switch has. Generally speaking though, KVM switches range from 2 to 64-port models, thus allowing for between 2 and 64 computers to be connected to a single KVM device, and in turn just one set of keyboard, monitor, and mouse.

For those KVM switches that support expansion capability, the more sets of ports a KVM switch has, the bigger the installation it usually goes in. For example, a 4-port KVM is ideal for a desktop, while an 8, 16, or up to 64-port KVM switch is best suited for a server room.
In addition to keyboard, monitor, and mouse, audio and USB peripheral-sharing capabilities can also be built into KVM switches.

There are other kinds of KVM switches as well for various applications, such as:

Over-IP KVMs for remote server management
Matrix KVMs or over-IP KVMs for control room applications
Multi-viewer KVMs for control centers and video editing
Multi-display KVMs for financial, banking, trading desks
Secure KVMs for government and military agencies
Special KVMs for production lines

Conclusion

To sum up, a KVM is a device that allows one to quickly and easily switch between multiple PCs or servers from a single console (keyboard, monitor, mouse setup) for greater efficiency, management, and both cost and space saving.
Common scenarios in which a KVM switch is useful include:

Home Office
Small businesses
Computer rooms and server rooms
Data centers
Control rooms
Manufacturing facilities

The above might seem like a lot of information at first, so it’s more important to decide why you’re interested in a KVM switch: Do you want to use it in a home office, a small business, or even for gaming? Are you trying to improve on cost efficiency and space saving in a server room? Do you need to monitor a data center from anywhere, even from the other side of the world?

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