Abstract: In this construction there are provided: a case; several contact members exposed within the case; several lead terminals electrically connected to some of the contact members, and a support member, all insert molded in the case and protruding outwards; and a circuit breaker provided outside the case, one of its ends supported by a lead terminal and its other end supported by the support member. Thereby compact and efficient unitary construction are attained, and space within a device to which this construction is to be fitted, can be economized. The contact members may be five in number, and may be arranged within the case for contact in a linear relationship, alternatingly serving as input side and output side contact members, with the end ones and the middle one serving for being switched between while the other two serve as common contact members.