The disc coils (1) are in parallel or in series. Each disc consists of two halves, of which one is wound in one direction and the other in the opposite direction after connection of the ends (3, 4) on turning of the socket, or the housing. Pref. the starts of the first half-coil (3) and the second one (4) are connected with a low transient resistance and the joint is located in the body of the insulating separation wall (1) between the two halves of the disc coil.
