Method and apparatus for inductively receiving cab signaling on board a

Abstract

A cab signaling apparatus for use on board a railway vehicle which is propelled on rail tracks by an electric drive motor. The invention utilizes a cab signal transmitted to the vehicle through a track circuit in the rails. On board receiving of the cab signal is done by a receiving coil, which may be mounted in front of the lead axle, as a current transformer around the lead axle, or at another location where the cab signal current is relatively strong. The cab signal that is sensed has a cab signal component and an interference component. On board the vehicle a sampled signal is taken which has the characteristic of the electromagnetic interference subjected to the cab signal receiver coil. The sampled signal is then subtracted from the sensed cab signal such that the sampled interference signal cancels the interference component of the cab signal. Embodiments include placing the sampling device as an inductive coil behind the lead axle and in other embodiments in front of the lead axle above the cab signal sensing coil. A series arrangement with selective polarity on the coils permits a vital arrangement. In some embodiments the sampling to achieve a sampled signal characteristic of electromagnetic interference is done by using a current transformer coil on the electric drive motor cable.