Usually it is on, When on fire, smoke (temperature) sensors output electricity signal(DC24V)throughcontrol center, and the electromotor in the actuator acts, valve is automatically closed, outputs the close electric signal.
Direct current electromotor drives to reset after valve acting.
Valve can be manually closed and reset, or be closed when fuse numbered 70℃.
The valve have six gears of adjustable air volume damper.