A pantograph (or "pan", or "panto") is an apparatus mounted on the roof of an electric train, tram, or electric bus to collect power through contact with an overhead line. Battery electric buses and trains are charged at charging stations. It is a common type of current collector. Typically, a single or double wire is used, with the return current running through the rails. The term stems from the resemblance of some styles to the mechanical pantographs used for copying handwriting and drawings.