Here is an old type KVM switch, PS/2 & VGA interface.
Top removed from the main body, the cables coming in from the bottom connect to the VGA, keyboard & mouse ports on the slave computers, the connectors at the top connect to the single monitor, keyboard & mouse.
PCB removed from the body. This is driven by a PIC16C57C-04 microcontroller.
The pair of LEDs indicate which computer is using the peripherals at any one time.