Abstract: A "snow brake" control system for a railway vehicle in which an electronic timing circuit is operative in response to the operator's brake valve device being moved to its brake release position to provide an output signal that acts through a relay switch to deenergize a magnet valve that normally interrupts communication of "snow brake" control pressure to the system relay valve in order to withhold "snow brake" operation for a predetermined period of time sufficient to allow the vehicle brake units to release the brakes and thereby effect operation of the brake unit slack adjuster mechanism. When the time period expires, the timing circuit output signal disappears and the magnet valve becomes energized to reestablish "snow brake" control pressure during the remainder of the brake release period to maintain a light brake application in effect.

Abstract: A dynamic/friction brake blending control system in which a brake pipe pressure responsive control valve device provides a friction brake pressure that is connected to the vehicle brake cylinders via a blending relay valve device having a self-lapping piston valve assembly spring biased to a brake application position in which the friction brake pressure from the control valve device is relayed unmodulated to the brake cylinders in the absence of dynamic brake effort on the vehicle. A control piston of the piston valve assembly is subject to the friction brake pressure from the control valve, while a friction brake feedback piston is subject to the friction brake pressure connected from the blending relay valve to the brake cylinders. These pistons act on the piston assembly in opposite directions and have equal effective pressure areas.