The abbreviation KVM stands for Keyboard - Video - Mouse. KVM products connect computer workstations with the participating computers. A KVM switch allows you to control multiple computers with just one mouse, a keyboard and a screen. The KVM switch acts as a switch that connects a set of devices with multiple computers. Depending on the type of KVM switch to USB devices and speakers can be shared.

KVM switches differ in the number of computers that can connect the user. Depending on the variant can be controlled from a single workstation between two and 64 computers; Some KVM switches can also chain ( cascade ) to reach a larger number of controllable computers. When cascading the computer port is forwarded a KVM switch to another KVM switch.

Monitor, keyboard and mouse are connected directly to the KVM switch. To connect the KVM switch to the computers that it serves, there are in addition to standard cables with VGA 2 × PS / 2 ( newer with DVI and USB ) proprietary cable (eg with DB25 connectors on the KVM switch ) with the advantage that the connection faster to produce and mechanically stable, and there are KVM switches with modular connectors that use an adapter on the respective ports per computer, so for the line between the same types of cables can be used as for Ethernet.

Switching is done by means of buttons, rotary switches or hotkeys ( shortcut key or double pressing a specific key on the keyboard). The KVM switch (except older, purely mechanical switch ) provides the emulation of keyboard and mouse that the computer connected to perceive both devices continuously as connected, and that their settings are stored separately for each computer. This avoids errors in the operating system or drivers and hardware. Almost all KVM boxes signal by LEDs or numeric displays, is which computer just worked.

For workplaces with two or four screens there are special KVM switches for dual or quad video video. Other models can be coupled with each other to this end and switch so synchronously.

Larger KVM switches for applications such as data centers have connections for two or more jobs and allow simultaneous work of several users / administrators on different computers. Such devices are " multi-user KVM switches " or " Matrix KVM Switches" called. The simultaneous access of multiple administrators on the same computer is often undesirable and can be limited using the configuration therefore. Devices of this size have a sophisticated security system with password protection and restriction of individual users on specific hosts. The selection of the computer takes place in large systems via OSD menus which show the previously configured name of the computer. The configuration is done via the OSD menu.

KVM over radio is still in the development stage.

KVM connections over a network

KVM over IP (KVM over IP, IP KVM) is particularly important in the professional field. For a switch with KVM over IP technology, keyboard, monitor and mouse are not connected directly to the KVM switch, but on a networked PC ( remote client ) with Java -based browser or special software. This communicates over TCP / IP networks with the KVM over IP switch to which the computers are connected. The switch relies around the screen output of the computer (encoder) and transmits it to the remote client (Decoder ) which is sent in the reverse direction, the keyboard and mouse information to the switch. KVM over IP allows control of the connected computer without physical access to the KVM switch, and therefore remote from any workstation in its own network or over the Internet - in some devices also via modem or ISDN. This are in the transmission elaborate safety measures required (high levels of encryption ). Disadvantages compared to conventional KVM technology are: Slow screen drawing, a limited color depth, a jumpy mouse movement and the (still) higher costs.

Compared to conventional methods of Fernadminstration via software such as VNC or Terminal Server, a KVM switch has the advantage that it also provides access, if the appropriate software component is not running for remote administration on the remote computer. Thus, for over a KVM switch also BIOS settings of remote computers change.

The leading manufacturer of professional IP KVM are Raritan, Minicom, Avocent, Belkin, Aten and OpenGear.

Operating System Support

KVM Switches learned only with the rise of the Microsoft operating systems Windows 2000 and Windows 2003 Server environment in the wide dissemination. These operating systems can not be controlled satisfactorily without a keyboard, monitor and mouse. In the traditional environment of the Unix server KVM switches are not used because these computers genus can be completely remote controlled via a simple text console on the network or even over the serial interface.

Modern, digitally operating KVM over IP switches are optionally equipped with a feature called Virtual Media. This enables administrators to transfer data between your local PC and remote servers, and so do a variety of tasks from their desks. These include the implementation of diagnostic tests and patching of operating system and application software. It does not matter what platform to base the different computer and operating system running on it.

KVM Splitter

The counterpart to the KVM switch, the KVM Splitter (CPU sharer, reverse KVM switch ). Such a switch provides the ability to connect multiple consoles (consisting of keyboard, mouse and monitor) to a computer. This is useful, for example, if a PC in several places ( jobs ) to be made ​​available.

KVM Extender

To increase the allowable distance between the computer and the KVM switch or of that between the KVM switch and work there are KVM extenders which transmit the keyboard and mouse signals without interference, and the video signals without too much loss of quality over greater distances than this would be possible without reinforcement.

In contrast to a pure amplifier for the signals of other cable types in particular Cat5 cable can this often be used with modular connectors ( colloquially RJ45), as used in Ethernet ( 100BaseTX or 1000BaseT ). Therefore, the most anyway existing or needed infrastructure can be used more flexibly, namely the extension of KVM cables. Note that this cable ( eight wires) are fully occupied for this purpose, the simultaneous use of Ethernet or TCP / IP is not possible, unlike KVM over IP (see KVM connections over a network). Depending on the cable length and specifications from the manufacturer, a larger cable cross-section are used as required for Ethernet to limit the signal attenuation to acceptable levels.

At the two ends of the conduit, a device is connected, depending, typically once a transmitter and one a receiver device. Both have to fit together, so they are usually sold as a pair.

A KVM switch may also contain one or more KVM extender. In addition, you will also need each have a receiver or transmitter for the other end of each line.

KVM management systems

KVM management systems take all the approaches together to computers via KVM-over- IP devices in a standardized user interface. The integrated rights management ensures that each administrator to the user only sees the computer, and can select for which it is responsible. In addition, power switches -over-IP can be included in the management system, so are the administrators with the KVM connection all Power switch functions for the selected computer.