The SM-200 Servo Drive is an automatic flight control system power unit. When coupled to the servo drum and housing assembly, the SM-200 controls aircraft aileron, elevator, and rudder surface position. The function of the SM-200 is to translate electrical inputs into a rotational mechanical output to drive a drum and housing assembly. The SM-200 also provides position and rate feedback signals.  The SM-200 requires an input voltage of +28 Vdc. The starting input wattage for the SM-200 is 60 Watts but is only 40 Watts while running.

The SM-200 is composed of a motor-tachometer, synchro (except for -94X and 95X units), and a clutch. The motor-tachometer is externally mounted on a cast aluminum housing that contains a bearing-supported gear train. The synchro, when present, and the clutch are externally mounted on a plate that serves as a cover for the housing. The SM-200 mounts onto a SB-201 mounting bracket for installation. The dimensions for the SM-200 are 7.55 inches in length, 3.75 inches in width and a height of 3.80 inches weighing 5.1 pounds maximum.