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. An LED indicates the On/Off status of the output relay
![A421 Johnson Control Valve](https://digitalassets.reecegroup.com.au/m/ff0024469d83aedf/Web_280x210-A421-Johnson-Control-Valve.jpg)
![A421 Johnson Control Valve](https://digitalassets.reecegroup.com.au/m/ff0024469d83aedf/Web_1200x900-A421-Johnson-Control-Valve.jpg)