Patent ID: 8283916
Filing Date: 2012-10-09
Classification: B01J,B01L,B07C,B82Y,G06K

Abstract:
1. Apparatus for writing a code onto a magnetic tag having a plurality of magnetically switchable elements for storing said information, said elements being separately switchable at different strengths of an external applied field, the apparatus comprising: means for writing a code onto said magnetic tag by applying a set of external applied fields to said tag, each field of said set of applied fields comprising a field of sufficient strength to switch ones of said elements having switching strengths equal to or less than the field strength, said applying comprising applying said fields in turn from a strongest field to a weakest field, whereby after each said field application successive said elements are switched to a magnetic state which is substantially unaffected by subsequently applied fields of the set, wherein each of said plurality of magnetically switchable elements has a different coercivity such that said plurality of magnetically switchable elements are addressable for writing using a ladder of magnetic fields of successive field strengths.