An airtight seal on these switches blocks out dust, dirt and moisture. They maintain your surface’s temperature by turning equipment on or off when they reach a set temperature. These switches actuate when the temperature rises to the setpoint and reset when the temperature falls below the reset point. Since they're SPDT (single pole, double throw) switches, they control one circuit and can either be wired to turn one device from on to off (normally closed) or from off to on (normally open). Wire them normally closed to power a heater—when the temperature rises to the setpoint, the heater will turn off until the temperature falls below the reset point. Or wire them normally open to turn on alarms or other devices when the temperature rises above the setpoint. Their setpoint isn’t adjustable, so they’re easy to set up and there’s no risk of unintentional changes.