A421 Johnson Digital Controller

The a421 series controls are single stage, electronic temperature controls with a single-pole, double-throw (SPDT) output relay. The controls feature an adjustable backlit LCD for viewing the temperature and status of other functions and a three-button touchpad for setup and adjustment. A LED indicates the on / off status of the output relay. The a421 control is 120 vac. The a421 controls provide heating or cooling control, sensor offset, temperature setback, adjustable anti-short cycle delay and a restricted user adjustment mode. The temperature units can be displayed in f or c. The temperature adjustment range is -40 to 212f or -40 to 100c. The a421 automatically changes from heating and cooling.