The A421 Series Electronic Temperature Controls are single-stage controls with a single-pole, double-throw (SPDT) output relay, a bright backlit LCD, and a three-button touchpad interface that can be set up to restrict user adjustments. An LED indicates the output relay's On/Off status. The A421 Series Controls have simple On and Off temperature settings for heating or cooling, an adjustable anti-short cycle delay, and a temperature offset function. The control range is -40 to 212°F (-40 to 100°C) for standard models. Models with a control range of -40 to 248°F (-40 to 120°C) are available in quantity orders. The controls feature remote sensing capability and interchangeable sensors. The A421 Controls are available in either Type 1 (NEMA)/IP20 high-impact plastic enclosure suitable for surface or DIN rail mounting or Type 4X (NEMA)/IP66 watertight, corrosion-resistant surface mount enclosures. A421 Controls with Off-Cycle Defrost (A421ABD and A421AED models) provide off-cycle defrost control with user-configurable defrost cycle duration and frequency.