In systems management, out-of-band management is a process for accessing and managing devices and infrastructure at remote locations through a separate management plane from the production network. OOB allows a system administrator to monitor and manage servers and other network-attached equipment by remote control regardless of whether the machine is powered on or whether an OS is installed or functional. It is contrasted to in-band management which requires the managed systems to be powered on and available over their operating system's networking facilities.
An out-of-band management device
A KVM switch is a hardware device that allows a user to control multiple computers from one or more sets of keyboards, video monitors, and mouse.
Mechanical switch for keyboard (serial, PS/2 connector) and video (VGA, DE-15 connector)