The cigarette lighter socket is an electric system used in automobiles for lighting cigarettes and to supply electrical power through a plug or a power adaptor (which may change the voltage; see below). However, they were not originally designed to provide electrical power for miscellaneous devices, and are not an ideal power connector for several reasons: notably the fact that three sizes exist (two for 12-volts DC and one for the older 6-volt DC systems) and the mating of the different sized 12 volt DC plugs and jacks is problematic. This, combined with the often only loosely secured connections (often using only friction and springs to make the connection hold), together with the low-current small-gauge wiring sometimes used, mean that the power connections they provide are sometimes unreliable and not suitable for high-power devices.