LONDON (June 13)—Groupe Michelin has licensed an acoustic wave technology from Transense Technologies P.L.C. for use in tire pressure warning devices, but the tire maker did not disclose how it intends to implement the technology. The Transense sensor uses surface acoustic wave (SAW) technology in a diaphragm that is placed between the side of the sensor subjected to tire pressure and a sealed reference chamber. Changes in tire pressure cause the resonant frequency of one device to increase while the second device will decrease. The change in the difference between these two frequencies is directly proportional to the difference in pressure of the tire and reference chamber. The sensor, about half an inch in diameter, is placed in all four tires and alerts the driver of a change in tire pressure. Transense said it has signed a worldwide licensing agreement with Michelin allowing the French group exclusive use of its SAW technology and to license it to other tire companies.