Abstract: An electric traction current-collector has a carbon current-collector block (1) housing a rupturable tubular container (7 l ) for air under pressure applied through a pneumatic control system for a pantograph or other carrier so that loss of air pressure due to rupture of the container causes the current-collector block to be retracted. The container (7) is so thin that, if it is not completely housed and supported, it bursts under the applied air pressure and consequently any defect in the carbon block which spoils complete support of the container causes retraction of the current-collector.