Accumulator air pressure Return Hydraulic pressure Emergency brake valve Hydraulic system pressure Pilot’s pedals Shuttle valve Shuttle valve Normal  anti-skid valves Fuse Autobrake pressure control Emergency IR cylinder Normal brake metering valve Alternate brake metering valve Alternate antiskid valve Air/oil transfer tube Brake accumulator Brake check valve Power brake control valves Antiskid control valves Shuttle valves Brake assemblies B A Figure 13-97.  The orientation of components in a basic power brake system is shown in A. The general layout of an airliner power brake  system is shown in B.  NOTE: In the segmented rotor brake section above, a brake  assembly was described that had alternating pistons supplied  by independent hydraulic sources. This is another method of  redundancy particularly suitable on, but not limited to, single  main wheel aircraft.  In addition to supply system redundancy, the brake  accumulator is also an emergency source of power for the  brakes in many power brake systems. The accumulator is  pre-charged with air or nitrogen on one side of its internal  diaphragm. Enough hydraulic fluid is contained on the other  13-57