Power transmission from the overhead line to an electrically-powered rail vehicle or trolleybus is realised through a perfectly adapted system using different products made of different materials. Power is obtained from the overhead line via sliding strips pressed against the overhead line by a pantograph. Carbon brushes are used in the majority of cases for transmitting current to the collector of DC motors, while earthing contacts ensure transmission of electrical power from the chassis to the wheels, thus preventing current from flowing through the wheel bearings and damaging these.

All the components mentioned must withstand extremely sophisticated requirements. Stable transmission of high power levels until wear is encountered, high resistance to corrosion and excellent emergency running characteristics are required, sometimes under extreme climatic conditions, at high speeds and with provisions made for a very high degree of failure prevention.