Railway cab signal

An improved railway cab signal transmitter for transmitting a cab signal onto a pair of rails having an impedance bond between said rails at the transmitter end of a track circuit, said transmitter comprising:

• a transmitting circuit in parallel to said impedance bond;
• a code means for providing an electrical voltage cab signal at a preselected frequency to said transmitting circuit;
• and
• the reactance of said transmitting circuit being of a value such that said transmitter supplies said rails as a constant current source to said rails generally independent of the varying electrical load on said rails by the position of a track vehicle.

A railway track cab signal apparatus for connecting to a pair of rails in a track section having a first impedance bond at one end and a second impedance bond at a second end, said track circuit comprising:

• a cab signal transmitter connected at said one end having a transmitting circuit in parallel arrangement with said first impedance bond, said transmitting circuit to resonate with said first impedance bond at a preselected cab signal frequency and to produce such cab signal having a current level generally independent of the position of a track vehicle in said track section;
• said cab signal transmitter having a code means coupled to said transmitting circuit for providing a cab signal of said predetermined frequency;
• and
• a wayside receiver means coupled to said rails at said second end for receiving track signals from said rails.