SERIAL UNIT

PROBLEM TO BE SOLVED: To provide bi-directional and unidirectional selection switches respectively connected so that the outline shape of a case main body can be prevented from being made huge, and that high frequency wide band frequency characteristics can be prevented from being interrupted for a plurality of branch terminals mounted on a serial unit. SOLUTION: The case main body is provided with a main circuit housing chamber whose surface side is arranged with branch terminals, and whose inner part is mounted with a printed circuit in a depth direction; and sub-circuit housing chamber whose surface side is arranged with branch terminals, and whose inner part is mounted with the printed circuit board toward a direction in parallel with the surface of the case main body. The printed circuit board in the sub-circuit housing chamber is provided with distributing circuits and bi-directional and unidirectional selection switches respectively connected between the respective output sides of the distributing circuits and the branch terminals arranged in parallel.