A Cool Yule Tool. Fix holiday lights with a squeeze of a trigger. The Light Keeper PRO is the complete tool for fixing miniature light sets! A must for Christmas time. This all-in-one tool fixes most light sets in seconds by addressing the damaged bulb at the plug or at the socket. The LED Head Light helps visibility in light repair. 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.