Abstract: A tire pressure monitoring system identifies tire locations by recognizing that certain characteristics are unique to front-located tires verses rear-located tires as well as left-side tires and right-side tires. A control circuit is coupled to a temperature sensor and an accelerometer for each tire to receive information processed to discriminate between left and right and front and rear tires, respectively. With this information and a pressure signal, the monitoring system provides the operator with tire location and pressure information without reprogramming upon tire rotation. The system also alerts the operator to run-flat tire operational constraints.

Abstract: An electronic compass system of the present invention includes a sensor for detecting the earth's magnetic field and for providing electrical signals representing the direction of the vehicle, a heading indicator for indicating vehicle headings in response to received vehicle heading signals, and a processor coupled to the sensor for receiving the electrical signals and coupled to the heading indicator for supplying the vehicle heading signals to the heading indicator.

Abstract: A warning system automatically alerts a vehicle operator to the fact that the next available exit should be taken for a desired or necessary service such as refueling. The system includes a source of information providing the current vehicle location as well as a source of information identifying the location of available selected service locations closest to each of the next two exits of a limited access highway. The system in a preferred embodiment includes a source of information indicating the available range of the vehicle (distance to empty or D.T.E.) and a microprocessor for calculating when the driver should take the next available exit to reach the desired service. The system further includes a suitable alarm which may be an audible alarm, a visual alarm or both to alert the vehicle operator that the next available exit should be taken.

Abstract: A vehicle compass system having a magnetic field sensor coupled to a processing circuit which samples the sensor data and implements a calibration routine that generates compensation signals to compensate the sensor for the effects of vehicular magnetism so that accurate heading information can be displayed on a display coupled to the processing circuit. If the signal levels detected are outside of a variable threshold, then the calibration routine is run. Also provided is a circuit for receiving vehicle position information in response to which the processing circuit adjusts the signals supplied to the display in order to account for magnetic variations between the true north and magnetic north.

Abstract: A wireless system for monitoring vehicle parameters, such as tire pressure, using radio frequency (RF) signals transmitted from transmitters close in proximity to an associated parameter sensor, to a centrally located receiver. The transmitted RF signals from the transmitters may be distinguished by the frequency of the respective transmitted RF signals. To detect the presence of an RF signal having a particular frequency, the wireless vehicle parameter monitoring system of one embodiment includes a digitally controlled tuner or a plurality of parallel bandpass filters, which pass different ranges of frequencies corresponding to the frequencies of the RF signals output from the transmitters. In this manner, RF signals transmitted from different tires may be distinguished based upon the frequency of the transmitted signal. The receiver of this system may be implemented in the receiver of a trainable transmitter such that a dedicated receiver need not be provided.

Abstract: An electronic vehicle theft detection system employing a magnetic field sensor for mounting within a vehicle to provide signal information representing the earth's magnetic field. The sensor is coupled to an electrical processing circuit for sampling the data provided by the sensor and for generating a theft alarm signal when the heading of the vehicle has changed due to unauthorized movement of the vehicle.