US Patent 7367634 Relay configuration for an electro-pneumatic train

A relay valve configuration which can be used with various cars in an electropneumatic train and under the control of one of the electropneumatic brake control valves. The improved brake control valve includes a relay valve mounted at an interface of the manifold. The valve has a source inlet connected to the reservoir interface port, an inlet connected to atmosphere, an outlet connected to the brake cylinder interface port and a control inlet connected to the exhaust interface port. The valve is responsive to the control inlet connected to the exhaust interface port to selectively connect the brake cylinder interface port either to the reservoir interface port or atmosphere. The exhaust interface port in AAR is known as the retainer port. A check valve/choke is also mounted on the manifold of the interface and is in the same housing as the relay valve.