State feedback control of switching server flowline with setups

A prismatic (18) having a square cross-section is provided in a rotation shaft (16) to which plug terminals (14) are fixed. The rotation shaft (16) is sandwiched between a pair of elastic pieces (17a), (17a) of an elastic holder (17), so that the respective elastic pieces (17a), (17a) are brought into contact with plane surfaces of the prismatic bar (18) parallel to each other. Therefore, an interval between the two elastic pieces (17a), (17a) of the elastic holder (17) is increased when the square bar (18) rotates, so that a firm and steady touch of a click can be provided.