jumper : Computer Hardware Buyers’ Glossary
In older hardware you configure it by shorting out pairs of pins with a conducting
bridge called a jumper. You select which port addresses to
use, IRQs (Interrupt Requests)
etc. Jumpers are usually black, blue or red. In more modern equipment you configure
with softare or the hardware is self configuring. Motherboards still make extensive
use of jumper to set clock speed, memory type etc. Various combinations of jumpers
over pins encode the different possibilities.