An apparatus for shutting off the hydraulic supply of a power tong when the door is opened comprises, in part, a ring gear and cage assembly having a throat. The ring gear and cage assembly are driven by a motor having a hydraulic supply. A door is mounted on a pivot on the ring gear and cage assembly for movement to open and close the throat. A cable is secured to the door at a point that is offset from the pivot. The cable extends through a sleeve to a valve end of the cable. A valve at the valve end of the cable has a valve housing and is operable by movement of a valve control to disengage the hydraulic supply from the motor. The valve end of the cable is connected to the valve control and the sleeve is connected to the valve housing.