Abstract: The internal electric fans for circulating and removing cooling air for electronic equipment and the power supply are mounted on fan and power supply drawers which are guided into and out of position in the cabinet for the equipment by pairs of spaced parallel guide rails, respectively. When the cabinet protects an electronic contention switcher having a plurality of computer ports, the computer ports are constituted by elongated socket connectors which are all mounted at an angle to the vertical.

Abstract: In order to be able to adapt an electronic circuit board apparatus designed for a particular IC chip configuration to accept other chips to perform the same function, the socket for the IC chip is provided with a set of jumper terminals coupled to selected ones of the socket so that in the event the IC chip for which the IC chip was designed is not available, the circuit board can use other IC chips by connecting the jumpers to in effect redefine the socket. In addition, redundant parallel circuitry and IC chip sockets can be provided on the circuit board with each IC socket being wired to accept a variety of functionally identical IC chips.