Front Diagnostic Lights;Simplified Wiring;Switchable Priority (Switching Relay);Built-in Priority Protection (Switching Relay);Premium Sealed Relays;Compact Design;Fuse Protected (with spare);100% Factory Tested;Isolated End Switch;Contractor Friendly PC Board Layout;Universal Thermostat Compatibility;24 Volt Power Output for hard wired thermostats;Field Replaceable Transformer;UL Approved