National Semiconductor Corporation

Gould Inc.

Gregory W Ledenbach

Dennis E Morris

David A Betts

An abnormal tire profile indicating system comprising a telemetry unit mounted on each wheel of a vehicle and a central receiver. Each telemetry unit comprises a piezoelectric transducer which is deflected with each wheel revolution when the tire profile is low. Deflecting the transducer produces an electric pulse. The transducer pulses are accumulated on a charge storage capacitor to provide a power supply. When the level of charge on the capacitor reaches a predetermined level, a counter commences counting the transducer pulses. When a predetermined number of pulses are counted, the counter renders a transistor conductive, which transistor connects the power supply capacitor to an encoder and a transmitter. The encoder produces encoded signals and resets the counter after a predetermined number of encoder signals are produced. The central receiver receives the modulated radio signals from each of the telemetry units. The counter limits the transmitter to transmitting only after a sufficient number of low profiles are detected to assure reliable operation and only after a sufficient number of wheel revolutions to meet FCC periodicity of transmission requirements. The reset counter limits the duration of transmissions to meet FCC requirements.

Low tire warning system

A system for recognizing a received encoded signal as being from a particular transmitter is disclosed. An encoder encodes a signal to have a predetermined sequence of pulses of three different predetermined sequence of pulses of three different predetermined durations within a constant bit interval in accordance with a trinary code; wherein each of the different predetermined durations corresponds to a different bit. A decoder is coupled to the receiver for recognizing the received encoded signal as being from the particular transmitter includes a programmable digital logic signal generator that is programmed in accordance with the trinary code for generating a programmed digital logic signal having a predetermined sequence of different digital words corresponding to the predetermined sequence of pulses of different predetermined durations in the transmitted encoded signal; a code converter for converting the received encoded signal to a decoded digital logic signal having digital words in accordance with the selected code by measuring and comparing the relative durations of the pulse and the non-pulse time during each bit interval; a comparator for comparing the decoded digital logic signal with the programmed digital logic signal; and a control logic circuit coupled to the programmable signal generator, the code converter and the comparator for synchronizing the programmed digital logic signal with the decoded digital logic signal and for recognizing the received encoded signal as being from the transmitter when said comparison indicates a predetermined number and sequence of valid comparisons between the decoded digital logic signal and the programmed digital logic signal.

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San Jose, CA, United States of America

Gregory W Ledenbach