one or more layers of control wires stranded on a central element surrounded by an outer jacket,

wherein said central element includes at least one pair of wires each wire of the pair of wires having a core element of a tension-resistant plastic, a layer of metal wires stranded on the core element, a layer of a compressible insulating material sheathing the stranded metal wires layer, where the wires of the pair of wires are stranded with one another with a length of lay of 20 to 40 D, where D is the outside diameter of the pair of wires, and where said central element is sheathed by a jacket of plastic.