<Li> Plug body diameter: 21.13--21.33 mm (median 21.18 mm) </Li> <Li> Most often used in European automobiles, and sometimes as a second socket in American automobiles expressly for DC power connections . </Li> <P> Plugs often include a pilot light LED indicator to indicate that electrical power is connected . Optionally, the plug may be equipped with an internal fuse for electrical safety, usually rated at 10 amps or less . In some designs, the tip of the plug may be unscrewed to reveal a cylindrical glass fuse; other variants may use a newer blade - type fuse inserted into the side or back of the plug . </P> <P> Since the cigarette lighter socket was originally designed only to heat a cigarette lighter, repurposing these sockets as generic power connectors can lead to many problems . In addition to the issues with partially - compatible physical dimensions, the plugs can vibrate out of the socket under normal driving conditions, owing to poor retention . Also, there have been reports of melted plug tips due to poor contact and heat generation from ohmic resistance . Non-vehicular use in stationary settings may avoid vibration problems when used as an alternative to 120 volt AC outlets, but low - quality connectors may still develop high resistance or intermittent contact . </P>

When did they stop putting cigarette lighters in cars