(under the class definition) Systems wherein each side of the supply circuit consists of at least a pair of conductors, the conductors on one side of the supply circuit being adapted to be connected to one pole of the source of supply, the conductors on the other side of the supply circuit being adapted to be connected to the opposite pole of the source of supply, at least three load devices being connected between these two pairs of conductors, at least one conductor of each pair of conductors on each side of the supply circuit having at least two load devices connected thereto, each of these two load devices being connected to different conductors of the pair of conductors on the other side of the supply circuit, so that by connecting one conductor on each side of the supply circuit to the source of supply, a selected one of the load devices may be supplied with current, for example: [figure] [figure]
