The Honeywell T775M2030 4-SPDT Modulating Temperature Controller (-40°F to 248°F) is a precision HVAC control device that regulates system temperature by modulating outputs through four single-pole, double-throw relays. It works by comparing sensed temperature to the setpoint and adjusting heating or cooling stages accordingly for precise climate management. Used in air handlers, heat... https://www.partshnc.com/modtempctrl-40248f-4spdt-2