A trouble light, also known as a rough service light, drop light, or inspection lamp, is a special lamp used to illuminate obscure places and able to handle moderate abuse. The light bulb is housed in a protective cage and a handle that are molded to form a single unit. It has a long power line for distant reaching; the handle may also have electrical outlet on it, allowing the light to also double as an extension cord.
Trouble lights are usually powered by AC wall current, but some are powered by a 12-volt source, such as a car battery. The bulb of the trouble light typically has a heavy filament to withstand dropping, and therefore is also referred to as a drop light. Newer models often use LED arrays as the light source. LEDS are more energy efficient, and may be more durable as well, compared to incandescents.
Trouble lights are intended to be used with "rough service bulbs", a form of incandescent light bulbs which are designed with as many as five support wires holding the filament to allow it to withstand heavy vibrations or movement. Lower voltage bulbs such as those intended to function with 12 volt power supplies also have a higher lumen output per watt of power consumption. Compact fluorescent lamps and recently, light-emitting diodes may also be used in trouble lights.
Trouble lights intended for use in hazardous areas such as in petrochemical plants will have features designed to prevent ignition of flammable gas around the lamp, such as heavy sealed lamp enclosures and guards to protect lamps from breaking.