Dimmer assembly, brass, watertight, 20 amp output, 0-120 VAC 60 Hz input, 0 - 140 VAC 60 Hz output. This Type W-20 autotransformer is mounted within an 8 x 10 x 5 brass enclosure per MIL-E-24142/6. The large plastic knob controls the output voltage in conjunction with the circular dial plate mounted on the cover.