Editing KVM switch (section)

== Use ==

A KVM Switch is a hardware device used in [[data center]]s that allows the control of multiple computers from a single keyboard, monitor and mouse (KVM).<ref>{{Cite web|url=http://www.raritan.com/landing/kvm-switch-selection-guide|title=KVM Switch Selection Guide|website=www.raritan.com}}</ref> The switch allows data center personnel to connect to any server in the rack. A common example of home use is to enable the use of the full-size keyboard, mouse and monitor of the home PC with a portable device such as a laptop, [[tablet computer|tablet PC]] or [[Personal digital assistant|PDA]], or a computer using a different operating system.

KVM switches offer different methods of connecting the computers. Depending on the product, the switch may present native connectors on the device where standard keyboard, monitor and mouse cables can be attached. Another method to have a single [[DB25]] or similar connector that aggregated connections at the switch with three independent keyboard, monitor and mouse cables to the computers. Subsequently, these were replaced by a special KVM cable which combined the keyboard, video and mouse cables in a single wrapped extension cable.  The advantage of the last approach is in the reduction of the number of cables between the KVM switch and connected computers. The disadvantage is the cost of these cables.

The method of switching from one computer to another depends on the switch. The original peripheral switches (Rose, circa 1988) used a rotary switch while active electronic switches (Cybex, circa 1990) used push buttons on the KVM device. In both cases, the KVM aligns operation between different computers and the users' keyboard, monitor and mouse (user console).

In 1992–1993, Cybex Corporation engineered keyboard hot-key commands.{{citation needed|date=June 2012}} Today, most KVMs are controlled through non-invasive hot-key commands (e.g. {{keypress|Ctrl|Ctrl}}, {{keypress|Scroll Lock|Scroll Lock}} and the {{keypress|Print Screen}} keys). Hot-key switching is often complemented with an on-screen display system that displays a list of connected computers.

KVM switches differ in the number of computers that can be connected. Traditional switching configurations range from 2 to 64 possible computers attached to a single device. Enterprise-grade devices interconnected via [[Daisy chain (electrical engineering)|daisy-chained]] and/or cascaded methods can support over 1,000 devices equally accessed by any given user console.<ref>{{Cite web |title=How does a KVM switch work? |url=https://www.eaton.com/us/en-us/products/backup-power-ups-surge-it-power-distribution/networking-and-kvms/kvm-switch-buying-guide.html |url-status=live}}</ref>