PURPOSE: To easily indicate the operating state of a linear actuation valve by fitting sensors into slots to detect the arrival of a follower stem when the follower stem moves vertically and to send information on a linear actuation valve from a remote position when the linear actuation valve is fully opened or totally closed.

CONSTITUTION: Sensors 15, 16 fitted to a front plate 9 by a group of slots 12, 13 and assembled in adjustable positions to allow a follower stem 6 to sufficiently approach its movement limit when a linear actuation valve 5 is fully opened or totally closed. The sensors 15, 16 can therefore detect the arrival of the follower stem 6 at either one of the ends of movement and send a signal indicating the fully opened or totally closed state of the related valve to a remote panel.