US Patent 7377158 Tire pressure sensor system with improved power saving

A battery powered vehicle tire pressure sensor system has a power saving unit which controls the application of electrical power to the system as a function of tire speed to prolong battery life. The power saving unit has a power control switch which is responsive to tire angular speed. Each sensor assembly of the system is mounted on or in the side wall of a pneumatic tire to generate signals representative of tire pressure whenever power is applied. A processor periodically samples the signals. When the processor determines that the tire pressure is outside a safe range, an r.f. generator is activated by the processor to generate an unsafe tire pressure signal. This signal is converted by a receiver to a warning for the driver.