The IR-2 provides the switching function to isolate two separate equipment controllers. The relay lets you function a single device with two independent controls and eliminates the possibility of power feedback. Plug the IR-2 control pigtails into each of the controllers you want to use to regulate your equipment. The center power pigtail operates the left outlet which is defeated when the control outlet is activated. Plug it into a timer or other control device or directly into wall receptacle.