Flying Null Limited

Christopher John Coggill

Michael David Crossfield

A magnetic marker or tag is disclosed which comprises (a) a first magnetic material characterised by high permeability, low coercivity and a non-linear B-H characteristic; and (b) a second magnetic material which is capable of being permanently magnetised, said first and second magnetic materials being superimposed one on the other and advantageously being substantially coterminous. The second magnetic material is preferably of medium coercivity. Selected regions of said second magnetic material can carry magnetisation such as to magnetically divide the first magnetic material into a series of magnetically discrete zones, the length of said magnetically discrete zones and/or the lengths of said magnetised regions (&ldquo;gaps&rdquo;) of said second material constituting elements of a code.

Multi-layer magnetic tag

A method of fabricating a tag or marker carrying or intended to carry a magnetic code is described. The method comprises applying a particulate magnetic material to a surface region of the tag by a printing or transfer process. The particulate magnetic material is generally deposited in the form of discrete elements or indicia. A tag thus produced can be coded magnetically by magnetising the elements or indicia, e.g. with a permanent magnet. This provides a very versatile and relatively rapid means of generating coded tags or labels virtually without limit on the variety of codes which may be adopted.

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West Wratting, United Kingdom

Christopher John Coggill