A low cost method for tire monitoring is designed using a passive LC circuit tag is used for contactless sensing. Circuit response to bursts of radio frequency pulses is made to vary with changes in tire pressure. Separate transmit and receive antennas are employed with a distance of about 100 mm. between the antennas and the LC circuit. A good clean signal is obtained with a significant reduction of signal level for a small variation of resonant frequency. The principles used in the system has the ability to detect changes in circuit performance which make it suitable for incorporation into a tire sidewall or tire valve.