DC-4 double check valve. P/N 278614. NSN 4820007287467. All ports are 3/8 inch female pipe. Used on various 2.5 and 5 ton trucks such as M35A2, M54A2, M809, M939 series.
Double check valves are used in an air brake system to
direct a flow of air into a common line from either of two
sources, whichever is at the higher pressure. They may be
used for directing air flow for specific functions or to select
the higher pressure of either of two sources of air as a