It is produced by the two Kepco power supplies. One drives the large coils, and the other the small ones, as stamped on their front panel. The output of each Kepco consists of four wires, two to lead the current, and the two others used for sensing. The four output plugs are located on the back panel of each power supply which can only be reached through the back panel of the rack. The connections are protected by a plastic strip and can not be touched by hands. In the hall, simple copper screws are used to connect those wires to the coils. They should never be touched. The grounding of the system is achieved in the hall.