The LightKeeper PRO is the complete tool for fixing light sets and pre-lit trees. This one tool offers two easy methods to repair your lights: a Quick Fix Trigger and an Audible Voltage Detector. Most holiday light set failures occur when an individual bulb 'shunt' fails to energize as a filament burns out. To correct this, the Quick Fix Trigger sends a harmless pulse of electricity through the circuit to find and fix the shunt, lighting the unlit section. The LightKeeper's Audible Voltage Detector allows you to easily scan and find the circuit interruption at a bulb, broken wire, or poor contact where the voltage is blocked. The detector will beep before the location of the block and will not beep after, pinpointing the problem. Other features include LED headlight, bulb puller, light set socket connector, 5 spare mini light bulbs, and a built-in storage organizer in the handle. Three 1.5V button cell batteries are included.