Officer technical specialists in ship machinery, electrical power, lighting, and interior communications systems. They supervise and instruct personnel whose duties involve operation and maintenance of main propulsion (gas turbine, diesel, or steam) and auxiliary machinery and systems, engineering and repair department equipment, and refrigeration systems; handling, stowing, and regulating expenditure of fuel oil and boiler feed water; installation, adjustment, testing maintenance, modification, and repair of shipboard electrical systems pertaining to power distribution, propulsion, steering, lighting, degaussing, interior communications, gyrocompass, and associated equipment, and instrument repair, adjustment, and calibration. An officer of the Naval Reserve.