Union Switch & Signal, Inc.

Anthony G Ehrlich

An improved railway cab signal transmitter for transmitting a cab signal onto a pair of rails for reception by a railway vehicle on said rails. A tuning arrangement is connected across the rails to generally resonate with the leaving end impedance bond at a preselected cab signal frequency. The cab signal is coded at the preselected frequency such that the resonant circuit acts in conjunction with the code signal generation to act as a constant current signal source feeding the rails. A reduction in the maximum cab signal rail current is achieved thereby mitigating runby cab signal currents which might be available for reception by following trains. Embodiments of the tuning arrangement use a capacitor on the primary winding of the feed transformer. Other embodiments include inductance in series with a capacitor. Receivers for wayside displays that also use the cab signal current include embodiments having a capacitor or a capacitor/inductor across the wayside receiver transmitter secondary.

Railway cab signal

A transmitter for transmitting cab signal and track signal currents to a pair of rails includes the circuitry for mitigating runby currents which are not fully shunted by the rail vehicle. High runby currents at the leaving end of a block are reduced by sensing the presence of a railway vehicle in the leaving end of the block. In response to sensing the rail vehicle the cab signal voltage is reduced to a lower level. The lower level and the position at which the railway vehicle is sensed are adjusted so as to permit a lead vehicle to receive at least a minimum cab signal value throughout its journey while assuring that following trains receive less than the minimum cab value required to activate the vehicle based receiver. The train is sensed by the voltage drop across the rails as the train approaches. A relay is used to respond to the presence of the train by applying a lower cab signal to the rails.

Railway cab signal transmitter

The invention provides a single-element coded alternating current railway track circuit which may be adapted to a double-element Phase-Selective configuration. A transmitter, via a transmitter transformer, provides a coded track signal to the track. A receiver transformer having one primary winding and a pair of secondary windings receives the track signal. One of the secondary windings is connected directly across a rectifier.The other secondary winding is connected in series with a secondary winding of a local transformer. This serial combination is electrically connected across another rectifier. A DC code-following relay is electrically connected across a rectified output of the first rectifier via two output terminals. A third output terminal allows substitution of a magnetic stick relay for the code-following relay if a double-element configuration is desired. The primary winding of the local transformer has terminals for connecting an AC source when using the optional double-element configuration.

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Pittsburgh, PA, United States of America

Anthony G Ehrlich