The ESD5500E Series speed control unit is an all electronic device designed to control engine speed with fast and precise response to transient load changes. This closed loop control, when connected to a proportional electric actuator and sup-plied with a magnetic speed sensor signal, will control a wide variety of engines in an isochronous or droop mode. It is designed for high reliability and built ruggedly to withstand the engine environment. Simplicity of installation and adjustment was foremost in the design. Non-interacting performance controls allow near optimum response to be easily obtained. The primary features of the ESD5500E Series speed control unit are the engine STARTING FUEL and SPEED RAMPING adjustments. The use of these features will minimize engine exhaust smoke experienced prior to attaining engine operating speed. Other features include adjustable droop and idle operation, inputs for accessories used in multi-engine or special applica-tions, protection against reverse battery voltage, transient voltages, accidental short circuit of the actuator and fail safe design in the event of loss of speed sensor signal or battery supply. The ESD5500E Series speed control unit is compatible with all GAC proportional actuators except the ACB2000 electric actuator. When the ESD5500E Series speed control unit is used with a ADC100 Series electric actuator, the DROOP adjustment range will be less due to this actuator's low current demand.