2-64. SYSTEM COMPONENTS (Continued).
RESERVE AIR RESERVOIR. Two reserve air reservoirs are used on M915, M916, and
M918; three on M917, M919, and M920. (See illustrations in para 2-65 thru 2-70.)
RELAY VALVE. Pressure from cab brake valves control flow of air from brake reservoirs
to rear axle brake chambers. Applies rear brakes faster and more firmly than if they were
actuated directly by air pressure in control lines from cab.