Frequency of defrost is one to six cycles per day. A minimum of four hours between successive defrost cycles. Adjustable back-up defrost termination from four-110 minutes in two minute increments. Control works with an external temperature or pressure sensor. Choice of three contact arrangements for electric heat, compressor shutdown or hot gas defrost. Positive switch action slider bar. Switch ratings per pole: 40 amp, 2 hp, 690 VA pilot duty, 120-240 volts AC. Heavy steel enclosure. Gray finish. Knockouts at bottom, back and sides. Hasp and staple for padlock. Available on bracket for sub-panel mounting. Operating voltage: 120 or 208-240 volt, 60 Hz (50 Hz - see chart below). Heavy duty, synchronous industrial type motor. First transfer after refrigeration cycle: (A633-20) 2-4 remains closed (compressor). 1-3 opens (fan). 3-N remains open (heaters). Second transfer: (3-6 minutes after the first) 2-4 opens (compressor). 1-3 remains open (fan). 3-N closes (heaters). Shipping weight = 3-3/4 lb. (1.7 kg.). Control supplied with 4 dial pins. Extra pins, part number X-3596.