A lead frame 10 includes first and second frames 13, 14 and a fixed contact piece 15. The fixed contact piece 15 is integrally formed with the first frame via a conductive connection part 16. The first frame and the fixed contact piece 15 and the second frame have installation parts 13a, 14a, 14b, 15b to which resistance elements are able to install. The first frame 13 and the fixed contact piece have installation parts 13b, 15a to which resistance elements are able to install. Electrical circuits of different types are formed through combinations of whether the resistance elements are installed to the respective installation parts and whether the conductive connection part 16 is cut off.