due to the action of orifice 24 the pressure in the bottom recess 23 and on the top face 19 of the piston will be equalized when this occurs piston 17 will move up in the cylinder due to the previously described differential areas on its top and bottom and eventually upward travel of the piston will cease when the element 18 abuts cylinder top wall 20 at this point the adjustable element 48 on piston rod 21 will have engaged the start button 47 of the integral three way control valve 16 this conventional valve now operates to place the in port 15 in communication with the out port 39 and the pressure fluid is conveyed through line 37 to the diaphragm chamber 38 of fuel or gas supply valve 35 opening this valve and admitting gas or fuel through line 34 to the machine 32 compressor engine or the like this permits the machine to operate in a normal manner if any of the malfunction sensors 29 30 etc reaches its preset stress point with regard to a variable such as pressure or temperature it will automatically vent to atmosphere through its valve 33 causing leakage at the particular sensing port 27 with which it is connected this leakage of pressure below the piston 17 will cause the piston to descend in the cylinder chamber because of the greater fluid pressure now acting on the.