Re: D&RGW tender air valves

JB:
I might be in error here in that the OM and OY don't use actual A-1 system because they use a K triple instead of the old style F triple used on A-1. But, yes, the adaptor is used between the triple (and H or a K) and the aux res. instead of the double check valve.
Mike:
The D&S uses a home brewed straight air application. They plumb the straight air into the retainer line (which is the exhaust of the brake cylinder when the brakes are released). There is a cut out cock to the retainer, and it must be closed to keep the straight air from simply going out the retainer. In order to use the retainers on the D&S, the straight air must be cut out and the retainer cut in.
Wabco's system allowed both systems to be used at the same time. It is rather rare and unique, and probably hard to find the parts for.