TEWA SPRAY FIRE PROTECTION TECHNOLOGY CO.,LTD. The OSY-1 supervisory switch is used to monitor the open position of an OS&Y (outside screw and yoke) type gate valve. OSY-1 supervisory switch shall be installed on each valve as designated on the drawing and/or as specified herein, 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.  
Supervisory switch shall have one form C contacts, switch contact rating 10.1Amps at 125/250VAC, 2.0Amps at 24 VDC.