Abstract: Apparatus for supplying electrical energy to a mobile working machine in the off-road sector, wherein a supporting arm is provided on the working machine, and a drum for accommodating a cable is mounted on the supporting arm. A slip ring body is arranged in the interior of the drum shell, the slip ring body having a plurality of individual slip rings, from which the electrical energy is taken via brushes and transmitted to a cable which is passed on into the working machine. The slip ring body is mounted so that it is separated mechanically from the drum casing on a common axis, and means are provided for transferring the revolution of the drum casing to the inner slip ring body.