Abstract: This invention relates to apparatus for periodically automatically purging the contaminants from a filter unit of a compressed air system to reactivate the filtering medium in the filter unit during the time that an air compressor for supplying air under pressure to the system is operating unloaded or is stopped.

Abstract: An anti-wheel skid brake control system including a control circuit for providing an impulse-like control current in accordance with which electro-magnetic control valves are operated to either release or reapply brake pressure in an intermittent fashion. The impulse-like control current displays a predetermined pulse form that may vary in duration and interval with different stages of a digital counter whose output is continuously monitored by a decoding logic network. The variable, impulse-like control current provides for a gradual change in the brake pressure during the final stage of brake release or reapplication during a wheel skid to accordingly avoid overshooting of the brake release or reapplication pressure.

Abstract: A system for each car of a railway train for detecting a hot journal box or boxes on the car by utilizing the heat of the overheated journal box to produce electrical current which, when a sufficient degree is transmitted through appropriate electrical devices to an explosive bolt placed in the brake pipe, causes the bolt to be exploded and thereby open a vent in the brake pipe to atmosphere to effect a brake application on the train. The sound of the escaping air from the brake pipe is used to determine the particular car on which the overheated journal box is located.

Abstract: A single relay serves to register route request selections for both traffic directions over each track route through a railroad interlocking layout. This single route request relay is jointly controlled by the route selection push buttons for both directions, the actuated push button being also repeated by a traffic direction relay. The route request relay pick up checks that no conflicting route request is active, and that the same or opposing route is not already established and locked. The route request and direction repeater relays are held by stick circuits to store the request until the route is locked. A single relay serves to provide the clear and lock function for all possible traffic routes originating at each entry point into the interlocking.