An identification system includes a clamshell device that grasps a wire, and a clip that secures the clamshell device in a locked and closed position. The headbody movement of the subject is recorded with markers placed on the shoulders and on the head and thus moving with the subject. Either the lower shading layer or the upper shading layer is, or both the lower and upper shading layers are, formed to have a convex shape and a sloped portion protruding toward the switching element. For this reason, by avoiding interference between exhaust flows from the two apertures, it is possible to suppress an abnormal sound caused by the interference. By detecting the continuous position, the phase information can be obtained from the table. The sleeve member includes a second tightening portion 27 and a first tightening portion 24 apart from each other in an axial direction.