A general purpose control system for use in the oilfield pressure pumping service industry. The system is comprised of a dedicated control computer mounted on the apparatus to be controlled and one or more remote operator units. The dedicated control computer interfaces with all the sensors and control elements of the apparatus. The control computer performs all the calculations necessary to control the apparatus. The dedicated control computer communicates with other computerized equipment on the apparatus such as engines, pressure sensors, speed sensors and flowmeters to extract data and perform control functions. The dedicated control computer has no operator controls. The dedicated control computer communicates via a single electrical cable to the operator control pendants. The control pendant is a small portable unit that provides the complete operator interface. The control pendant is comprised of graphic/alpha-numeric liquid crystal display and light emitting diode displays which provide the operating status of the system. The control pendant also includes key switches which are used for controlling the apparatus.