[en] A modular microprocessor system is used to control the Fermilab high voltage test facility. Operationally, the system has been patterned after typical Fermilab accelerator control systems. The operator can select pages of analog parameters and digital status to be displayed on an alphanumeric screen; analog readings or settings may be displayed either in engineering units or in volts; devices are selected for on/off or analog control by cursor position; an incremental shaft-encoder knob adjusts the value of analog parameters and digital time delays. Settings of parameters can also be entered from a 16-key keyboard and transmitted to the device. Two microprocessor systems are used--one in the high voltage equipment dome and one at ground potential. Communication between the processors is via two serial, digital, fiber optic light links