A semiconductor substrate includes a pair of trenches filled with a dielectric material. A free end of the contact arm is brought into abutment with a workpiece and a trigger is pulled for driving a nail thereinto. As a result, quality level of a video picture to be displayed on the liquid crystal panel is deteriorated. This promotes unlocking of the line and allowing the line to move in the first line releasing direction, engagement of the line by the cam to the line locking position creating a force couple which is a function of the predetermined distance, that tends to separate the frame from the support surface. Therefore, it is possible to easily check which communicating section is effective when communication regulation occurs, and hence the user can easily make a determination such as that alternative communicating section is used, or that communication is aborted.