Front Diagnostic Lights;Switchable Priority;Built-in Priority Protection;Simplified Wiring;Works with 2, 3, or 4-Wire Zone Valves;Compact Design;Fuse Protected;100% Factory Tested;Two Pump End Switches can control up to 3 pumps;System, Secondary and DHW;Contractor Friendly PC Board Layout;Universal Thermostat Compatibility;24 Volt Power Output for hard wired thermostats;Field Replaceable Transformer;UL Approved Extended