Cigarette lighter receptacle

The cigarette lighter receptacle in an automobile was initially designed to power an electrically-heated lighter for cigarettes. It was later used as a de-facto standard DC connector to supply electrical power for portable accessories used in or near an automobile. Examples of devices that can be operated from a cigarette lighter receptacle include lights, fans, beverage heating devices, and small motorized tools such as compressors for inflating tires. Many portable electronic devices such as music players or mobile telephones use a cigarette lighter receptacle to recharge their internal batteries or to directly operate from the vehicle electrical system. Adapters for electronic devices may change voltage to be compatible with the supplied device. Devices that require alternating-current power at 120 volts or 240 volts can be operated with a plug-in inverter. Currently, automobiles may provide several cigarette lighter receptacles that are intended primarily to operate accessories and are not to be used with a cigarette lighter.
While the cigarette lighter receptacle is a convenient and nearly universal feature of automobiles, as a DC power connector it has the disadvantage of relatively low current rating and poor contact stability.

Lighter

The traditional lighter is a metal or plastic cylinder containing a thin coil of nichrome wire, through which high current (~10 amperes) passes when the device is activated, usually by pushing it into the socket as though it were a button. When pushed in, the lighter is held against the force of a spring by a hook attached to a bi-metallic strip.[1] The heating element becomes glowing orange hot in seconds, causing the bimetallic strip to bend and unhook the mechanism, and the handle pops out. If the lighter is then promptly removed from its socket, it is capable of setting cigarettes, cigars and tinder (among other things) on fire.
In newer cars, the socket often ships with a plastic dummy plug, without the lighter heating element due to declining popularity (and legality) of smoking[2] However, the socket continues to exist to power consumer electronics in cars as the primary purpose. Often, a vehicle may come with several outlets for convenience, some in the rear passenger area of the vehicle. Even the cargo area may be supplied with sockets for such purposes as powering portable GPS devices, recharging telephones, or powering a tire pump or a vacuum cleaner. These usually have a plastic cap tethered to them, and are usually labeled as being only for DC power since they are not intended to withstand the heat produced by an electric cigarette lighter.

Plugs
Twelve volt automobile plugs are standardized in the United States by the "UL standard 2089" regarding vehicle battery adapters. This standard covers plugs and cord sets that insert into cigarette lighter receptacles. In Europe, 12 volt plugs and sockets are regulated and require approvals; see "e mark" for requirements.