Light Keeper Pro Tool. The complete Maroon Voltage Detector Tool to fix Incandescent Lights Sets. Great for pre-lit trees! Never been used.♡(Please Read.) More Info; The Audible Continuity Detector traces the circuit to the point of interruption. The 3-way bulb puller helps release tight bulbs from their sockets. The Bulb & Fuse Tester tests both indoor and outdoor mini lights. There is a spare bulb compartment in the handle for storage of extra bulbs and fuses. Three (3) 1.5-Volt Batteries are included. Patent pending. The trigger send a pulse that will activate a defective shunt; This fixes the circuit allowing the current to flow. Simply plug your Light Keeper PRO into the light set, pull the trigger and a pulse goes to the bulb, fixes the shunt and allows the light set to work correctly. The light keeper pro is not intended with led, rope or light set/sets with control boxes.