A KVM switch (with KVM being an acronym for Keyboard, Video, Mouse) is a piece of hardware that allows a user to control multiple computers from a single keyboard, video monitor and mouse. Although multiple computers are connected to the KVM switch, only one can be controlled at a time. Modern devices have also added the ability to share USB devices and speakers with multiple computers.
A user connects a monitor, keyboard, and mouse to the KVM switch, then uses special cables to connect the KVM switch to the computers. Control is switched from one computer to another by the use of buttons on the KVM switch, with the KVM switch passing the signals sport ween the computers and the keyboard, mouse and monitor depending on which computer is currently selected. Most devices also allow control to be switched through keyboard commands (such as hitting a hot key). Some KVM switches also send signals to the computers that are not currently selected to ensure that they do not think that the keyboard, mouse and monitor are dis-connected.
KVM Switches in the number of computers that can be connected, some man connect up to 64 computers. Enterprise-grade devices can also be chained to allow even greater numbers of computers to be controlled from a single set of a keyboard, video and mouse. A KVM switch is useful where there are multiple computers, but no need for a dedicated keyboard, monitor and mouse for each one. They are frequently used in data centers where multiple servers are placed in a single rack with a single keyboard, monitor and mouse. A KVM switch then allows personnel to connect to any server in the rack.