302 PC PASSENGER-BRAKE EQUIPMENT 



Chamber F, at the small end of the equalizing piston, is con- 

 nected to the atmosphere through the port t, cavity i in the 

 release slide valve, and the emergency-piston exhaust Ex, 

 thereby removing the pressure on the small piston that tends 

 to force the piston forwards. This makes the force of the pres- 

 sure, in chamber A , that tends to hold the big piston in position 

 greater than the force due to the pressure in chamber E that 

 tends to move the equalizing piston forwards, so that the piston 

 is held in the position shown. 



Chamber 5 is connected to the atmosphere through port j, 

 the cavity * in the release slide valve 4> and the emergency- 

 piston exhaust Ex. This removes the pressure on the lower 

 end of the small piston and makes the force of the pressure in 

 chamber P greater than the force, in chamber R, that tends 

 to move the emergency piston, so that the piston is held in 

 the position shown. 



The reduction-limiting chamber F is connected to the atmos- 

 phere through the port m, the cavity w in the slide valve 22, 

 and the reduction -limiting chamber exhaust w. 



The application chamber X and the chamber C ahead of 

 piston 78 are connected to the atmosphere through port /, 

 port I in the release slide valve 4. port I', and the application - 

 chamber exhaust. 



The service cylinder and chambers M and O are connected 

 to the atmosphere through ports n, em, and en, chamber O, 

 port k, and the service-cylinder exhaust. 



The emergency cylinder is connected to the atmosphere 

 through port o, the cavity in the emergency slide valve, port o', 

 and the emergency-cylinder exhaust Ex. 



The small cavity in the release 'graduating valve is con- 

 nected to the atmosphere through port and cavity in the 

 slide valve 4 and the emergency-piston exhaust Ex. This 

 relieves the face of the graduating valve of sufficient pressure 

 to insure the graduating valve being held firmly on its seat 

 under all conditions. 



Preliminary Service-Application Position. A reduction in 

 brake-pipe pressure lowers the pressure in chambers A and B 

 below that in chambers D and E, thus tending to move both 

 the pistons 20 and 3 forwards from release position. Piston 3 



