Modular input/output expansion system for an external computer

A stand-alone input/output (I/O) expansion system for an external computer unit, the system providing additional I/O circuit card capacity and controller support for the I/O circuit cards for the external computer unit, the system comprising:

• a rack,
• at least one I/O expansion module mounted to the rack, the I/O expansion module comprising at least one I/O circuit card and a housing having an extensible tray for selectively sliding the tray from the rack in a substantially horizontal plane between an extended position and a retracted position, the at least one I/O circuit card being received on the tray, the I/O expansion module further comprising a cable trough to facilitate passage of a series of cables connected to the at least one I/O expansion module to external of the I/O expansion system;
• a utilities control module mounted to the rack, the utilities control module having a clock generation printed circuit assembly for generating a clock signal for the at least one circuit card;
• and
• a power control module mounted to the rack, the power control module being electrically connected to a power source and being configured to distribute the power to the at least one I/O expansion module and the utilities control module.