The MA-OSY-1 supervisory switch is used to monitor the open position of an OS&Y (outside screw and yoke) type gate valve. MA-OSY -1 supervisory switch shall be installed on each valve as designated on the drawing. Switches shall be mounted so as not to interfere with the normal operation of the valve and shall be adjusted to operate with two revolutions of the valve control or when the stem has moved no more than one-fifth of the distance from its normal position.