A substrate includes a plurality of input ends, a plurality of output ends, first and second direct-current power lines, a first region and a second region. An alternating voltage is applied between any two of the input ends. The first region permits mounting of any one of a plurality of kinds of first surface-mount devices that selectively establishes electrical continuity between one of said plurality of input ends and either said first or said second direct-current power line. The second region permits mounting of a second surface-mount device that selectively establishes electrical continuity between one of said plurality of output ends and said first or said second direct-current power line.