2. Overhead contact line

A conductor wire placed in the axis of the track allows an articulated current collector, called a "pantograph", placed on the roof of the traction unit, to capture the energy to supply its power equipment (figure 2 ).

The contact line performs two essential functions:

• electrical: power distribution with the lowest possible ohmic resistance;

• mechanical: contact with pantograph exerting adequate pressure regardless of the impact of vehicle movement or contact wire.