A trouble light, also known as a rough service 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; doubling as an extension cord

Extension cord

An extension cord, power extender, or extension lead is a length of flexible electrical power cable with a plug on one end and one or more sockets on the other end . The term usually refers to mains extensions but is also used to refer to extensions for other types of cabling...

, the power cord often has an electrical outlet at the end of it.

Trouble lights are usually powered by AC

Alternating current

In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

 wall current, but some are powered by a 12-volt source, such as a car battery

Car battery

An automotive battery is a type of rechargeable battery that supplies electric energy to an automobile. Usually this refers to an SLI battery to power the starter motor, the lights, and the ignition system of a vehicle’s engine...

. The bulb of the trouble light typically has a heavy filament to withstand dropping. It is also referred to as a drop light.

Trouble lights are intended to be used with rough service bulbs, a form of incandescent light bulbs which have lamps designed with as many as five support wires holding the filament, designated as "rough service". 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. Fluorescent lamp

Fluorescent lamp

A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...

s and light-emitting diodes are also used to make trouble lights.

Trouble lights intended for use in hazardous areas

Electrical Equipment in Hazardous Areas

In electrical engineering, a hazardous location is defined as a place where concentrations of flammable gases, vapors, or dusts occur. Electrical equipment that must be installed in such locations is especially designed and tested to ensure it does not initiate an explosion, due to arcing contacts...

 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.

Applications

Trouble lights are often used in automotive service stations by automotive mechanics and electricians where localized light is needed where ambient light proves to be insufficient.

Trouble indicator

Another use of the term "trouble light" is an indicator for faults in a system, such as an automotive Idiot light

Idiot light

A tell-tale is an indicator of the status or malfunction of a system within a motor vehicle. Tell-tales consist of a light bulb or an LED which lights up a symbol or text legend...

 or a warning light of any kind, such as a Service Engine Soon light.