A tire pressure detector of an automobile, comprises a magnet having N and S poles and rotated in accordance with a pneumatic pressure in a tire, the N and S poles being rotatable in reverse, detecting means, arranged opposite to the magnet, for detecting magnetism and outputting a voltage signal...http://www.google.de/patents/US5814725?utm_source=gb-gplus-sharePatent US5814725 - Tire pressure detecting apparatus and monitoring apparatus
