TIRE CONDITION INDICATOR

An abnormal tyre condition indicating system comprising a telemetry unit (A) mounted on each wheel of a vehicle and a central receiver (B). Each telemetry unit (A) comprises a piezoelectric transducer (C) which is deflected with each wheel revolution when the tyre profile is low. Deflecting the transducer produces an electric pulse. The transducer pulses are accumulated by an accumulator D until a predetermined condition is met, such as stored charge reaching a threshold level. When the predetermined condition is met, the accumulator D produces an enable signal. The enable signal enables a digital encoder E to produce a digitally coded signal. A transmitter F modulates a carrier frequency with the digitally coded signal to produce digitally modulated radio transmission signals. The central receiver (B) receives the digitally modulated signals from each telemetry unit (A) and produces an indicia of the occurrence of the abnormal tyre condition at one or more of the wheels.