Abstract: A system for sensing current that includes a processor and a current sensor coupled to the processor. The current sensor includes a sensor threshold value. The system also includes a current generator coupled to the current sensor. The current generator is operable to generate a test current signal defined by a time-varying linear function. The current sensor is operable to be coupled to an external current source and to output a sensor output signal based on a detected current to the processor. The processor is operable to determine a magnitude of the sensor threshold value based on the sensor output signal.

Abstract: A system for sensing current, comprising: a processor; a current sensor coupled to the processor and including a sensor threshold value; and a current generator coupled to the current sensor; wherein the current generator is operable to generate a test current signal defined by a time-varying linear function, the current sensor is operable to be coupled to an external current source, the current sensor is operable to output a sensor output signal based on a detected current to the processor, and the processor is operable to determine a magnitude of the sensor threshold value based on the sensor output signal.

Abstract: A signaling and traffic control system which is capable of a vehicle determining its own absolute position along a guideway based on information received from the wayside using an inductive loop or beacon system in conjunction with the distance traveled according to the onboard tach generator(s), and report its position to a wayside control device, whereby the wayside control device reports to the vehicle, as part of its communications message, the location of the closest forward obstacle. Based upon this information, the vehicle controls itself safely based upon its characteristics as contained in a topographicla database and a vehicle database.

Abstract: An audio frequency (AF) track circuit whereby a railway track tuned loop transmitter operating in a dual resonant mode, for handling, two signal frequencies, can be coupled to the rails. Each frequency is conducted through a tuning unit having series and parallel branches tuned to each frequency. The track circuit using the tuned loop transmitter eliminates DC return current imbalance effects while maintaining suitably high track circuit shunting sensitivity.

Abstract: An interface system providing vital inputs to and vital outputs from a vital processor of railway signals for railway signalling and control purposes, utilizes non-vital components such as diodes and transistors. The input interface translates a railway signal, for example, from a relay contact closure of a track relay, into a multi-bit serial digital signal representing a restrictive state of the input railway signal in the event of any failure in the input interface. The output interface utilizes an absence of current detector having a saturable transformer coupled to an output line which provides operating current to railway signal and control devices, such as relays, switch machines and signal lamps.

Abstract: A railroad train detector and communication system relies on the track rails for communicating information among a plurality of locations. The equipment located at each of the locations eliminates relay based current detection, relay based current transmission, and relay based logic functions, and rather these functions are implemented with microprocessors. An extent of signal trackway is defined between a pair of head ends, intermediate the head ends at intermediate insulated joint locations, a microprocessor implemented transmitter/receiver pair is provided. One half of the transmitter/receiver pair manages communication flow for each direction of information flow at the joint. At each of the head locations, only a single transmitter/receiver is required. Associated with each microprocessor in a transmitter/receiver is auxiliary apparatus to couple the microprocessor's input/output ports to the track rails themselves.

Abstract: An audio frequency track circuit with improved security in the train detection function for rapid transit applications for use with uninsulated rails includes an improved transmitter and receiver. The transmitter modulates a track frequency carrier with a fixed code rate, regardless of the code rate employed to modulate the train information frequency. The receiver includes a decoder tuned to the track frequency modulation rate. By using such a sharply tuned decoder, the noise protection threshold is increased. Because of its application to uninsulated rails, with the associated lack of hard track circuit boundaries, adjacent track circuits have different track frequency modulation rates to insure that the modulated track frequency signal, from one track circuit, is not effective to operate a track relay in another circuit even under failure conditions.