A magnetic detection system for authenticating a document includes a first magnetic scanhead adapted to create a first magnetic field for saturating the magnetization of an area on each of the bills. The magnetic detection system further includes a second magnetic scanhead with an electromagnet. The...http://www.google.de/patents/US7591428?utm_source=gb-gplus-sharePatent US7591428 - Magnetic detection system for use in currency processing and method and apparatus for using the same
