Running Position gives air flow to the brake pipe as regulated by the feed valve. First Service Position is for use on long trains with maximum permissible leakage. This position provides an initial normal service rate of brake pipe reduction sufficient to initiate quick service on the train brakes, after which a slower rate is imposed, allowing the brake pipe pressure to readjust itself thruout the train and avoiding a heavy reduction at the front end. A maintaining type of equalizing piston is utilized to assure that this imposed rate is not exceeded. Lap Position is used while holding the brakes applied after a service application until it is desired either to make a further brake pipe reduction or to release brakes.
All ports are closed.
Service Position applies locomotive and train brakes uniformly on both a time and pressure basis. This is accomplished by the displacement reservoir, which delays the beginning of effective brake cylinder pressure development on the locomotive to coincide with that on the train. This adjustment is made by the rotair valve. Brake Pipe Cutout cock, located on the filling piece portion at the bottom. Forward position of the handle cuts the brake valve in.