Magic sensor. Coloured X-ray of a tyre fitted internally with an autonomous sensor (yellow). This long-lived sensor is powered solely by the changes in pressure it measures, needing no batte- ry. It is only active when there is a change to measure. Voltage is generated in its piezoelectric materials by changes in pressure. The voltage is converted into a radio signal, and this data is transmitted to an external receiver by an antenna. In this case, however, the sensor is linked by a wire. This sensor, which is being co-developed by Siemens, Germany, and Continental, will contin- uously check the tyre pressure while driving.