Abstract: Magnetically or optically detectable elements are arranged on a substrate so as to encode information to be stored. An information carrier comprises a plurality of individual detectable elements supported by, or incorporated in, a substrate wherein the spacing between the elements serves to encode the information and is such that it can be represented as A+MG, wherein A is a first fixed value, m is an integer (which may be zero) and G is a second fixed value, characterized in that the values of the integer m, are selected to be integers derived by a predetermined mathematical sequence or a random sequence generator.

Abstract: In a method of interpreting coded information carriers, a plurality of magnetic elements supported by, or incorporated in, a substrate, are interrogated. The relative positions and/or physical dimensions of the magnetic elements represent the information encoded by the information carrier. The relative positions and/or physical dimensions are determined from the relative velocity between an interrogating signal and each of the magnetic elements.

Abstract: A detector for reading information stored in a magnetic tag is disclosed, the reader comprising two assemblies of permanent magnets (each containing three magnets) arranged with their magnetic poles in opposition such that the magnetic poles of one triplet are physically opposite the like poles of the other triplet. The magnets are preferably elongate with their long axes being mutually parallel. The two magnet assemblies define between them a gap through which, in use, a tag having magnetic material is passed. Receiver coils are positioned within the gap. The magnet assemblies are preferably rigidly secured within an aluminum housing. Electrostatic screening foils may be placed over the receiver coils.

Abstract: Systems and techniques are disclosed wherein a method of providing a security code for a document comprises applying a first magnetic feature capable of being read by a contactless magnetic reader and having a fixed magnetic signature selected from a set of magnetic signatures, and applying a second magnetic feature capable of being read by a contactless magnetic reader and characterized by its magnetic signature and its spatial location on the document. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A method of sensing the position of a first element with respect to a second element is disclosed, the first element being movable with respect to the second. The method comprises: (a) fixing a first magnetic marker to said first element; (b) fixing a second magnetic marker to said second element; (c) sensing the positions of the two markers by a remote magnetic sensing technique. Optionally, a third magnetic marker may be used, the second and third markers then preferably being located at the extremes of travel of said first element. The method may be used to determine linear or angular relationships.

Abstract: A magnetic tag or marker is described which is capable of functioning as a multi-bit information carrying tag. The tag may be attached to an article and then used as a means of identifying that article, generally as it enters or is positioned within an interrogation zone. The tag comprises (a) a first magnetic material characterized by high permeability, low coercivity and a non-linear B-H characteristic; and (b) a second magnetic material which is capable of being permanently magnetized, the second magnetic material being magnetized with a non-uniform field pattern (A, B, C). Detection systems for use with such tags, and write/read system using them, are also disclosed.

Abstract: Magnetic tags or markers are disclosed, together with a variety of techniques by means of which such tags may be interrogated. In one aspect, the magnetic marker or tag which is characterised by carrying a plurality of discrete magnetically active regions in a linear array. In another aspect, the invention provides a method of interrogating a magnetic tag or marker within a predetermined interrogation zone, the tag comprising a high permeability magnetic material, for example to read data stored magnetically in the tag or to use the response of the tag to detect its presence and/or to determine its position within the interrogation zone, characterized in that the interrogation process includes the step of subjecting the tag sequentially to: (1) a magnetic field sufficient in field strength to saturate the high permeability magnetic material, and (2) a magnetic null as herein defined.

Abstract: A reader for interrogating a magnetic tag, e.g. for reading data stored in the tag, is described. The reader comprises a field generating device the magnetic field produced by which defines an interrogation zone, wherein said field generating device comprises: (a) means for generating a magnetic field: (b) a transmit coil for transmitting an interrogating electromagnetic signal into the interrogation zone so as to interact with a magnetic tag, when present in said interrogation zone; and (c) at least one receive coil for receiving an electromagnetic signal generated by a tag in response to said interrogating signal and the magnetic field produced by said magnetic field generating means. The field generating means can take the form of a pair of hollow cylinders, giving rise to a “loop” reader, or it can be a flat magnet, giving rise to a “side pass” reader.

Abstract: Magnetic tags or markers are disclosed, together with a variety of techniques by means of which such tags may be interrogated. In one aspect, the magnetic marker or tag which is characterised by carrying a plurality of discrete magnetically active regions in a linear array. In another aspect, the invention provides a method of interrogating a magnetic tag or marker within a predetermined interrogation zone, the tag compromising a high permeability magnetic material, for example to read data stored magnetically in the tag or to use the response of the tag to detect its presence and/or to determine its position within the interrogation zone, characterized in that the interrogation process includes the step of subjecting the tag sequentially to: (1) a magnetic field sufficient in field strength to saturate the high permeability magnetic material, and (2) a magnetic null as herein defined.

Abstract: Magnetic tags or markers are disclosed, together with a variety of techniques by means of which such tags may be interrogated. In one aspect, the magnetic marker or tag which is characterized by carrying a plurality of discrete magnetically active regions in a linear array. In another aspect, the invention provides a method of interrogating a magnetic tag or marker within a predetermined interrogation zone, the tag comprising a high permeability magnetic material, for example to read data stored of the tag to detect its presence and/or to determine its position within the interrogation zone, characterized in that the interrogation process includes the step of subjecting the tag sequentially to: (1) a magnetic field sufficient in field strength to saturate the high permeability magnetic material, and (2) a magnetic null as herein defined.

Abstract: Magnetic tags or markers are disclosed, together with a variety of techniques by means of which such tags may be interrogated. In one aspect, the magnetic marker or tag which is characterized by carrying a plurality of discrete magnetically active regions in a linear array. In another aspect, the invention provides a method of interrogating a magnetic tag or marker within a predetermined interrogation zone, the tag comprising a high permeability magnetic material, for example to read data stored magnetically in the tag or to use the response of the tag to detect its presence and/or to determine its position within the interrogation zone, characterized in that the interrogation process includes the step of subjecting the tag sequentially to: (1) a magnetic field sufficient in field strength to saturate the high permeability magnetic material, and (2) a magnetic mill as herein defined.

Abstract: A detector for sensing the presence of a magnetic tag having an axis of easy magnetization, which comprises (1) either (i) a magnet or (ii) a pair of magnets arranged in magnetic opposition, the magnet or magnets being disposed so as to define a spatial region through or across which the magnetic tag is, in use, passed, the disposition of the magnet(s) and the resultant magnetic field pattern being such as to cause a change in polarity of the magnetization of the magnetic tag in the course of its passage through a magnetic null within the spatial region; and (2) a receiver coil or coils positioned above and in proximity to one pole of the magnet (where a single magnet is employed), or positioned between the pair of magnets (where two magnets are employed) and arranged to detect magnetic dipole radiation emitted by a magnetic tag as it passes through the magnetic null with the easy axis of magnetization of the tag oriented in the direction of travel.

Abstract: 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 (“gaps”) of said second material constituting elements of a code.

Abstract: Magnetic tags or markers are disclosed, together with a variety of techniques by means of which such tags may be interrogated. In one aspect, the magnetic marker or tag which is characterized by carrying a plurality of discrete magnetically active regions in a linear array. In another aspect, the invention provides a method of interrogating a magnetic tag or marker within a predetermined interrogation zone, the tag comprising a high permeability magnetic material, for example to read data stored magnetically in the tag or to use the response of the tag to detect its presence and/or to determine its position within the interrogation zone, characterized in that the interrogation process includes the step of subjecting the tag sequentially to: (1) a magnetic field sufficient in field strength to sacurate the high permeability magnetic material, and (2) a magnetic null as herein defined.

Abstract: A surgical device, e.g. a catheter or a prosthesis, is disclosed which is characterised in that it carries, at a predetermined location, a tag formed of a high permeability, low coercivity magnetic material. Also disclosed is a method of locating a surgical device within the human or animal body, which comprises inserting the device into the body together with a magnetically active marker, the marker being associated with a predetermined location on the surgical device; and sensing the position of the marker, and hence of the surgical device, by remotely detecting its magnetic response to an interrogating signal. Systems for use in this method are also disclosed.

Abstract: An improved EAS tag is disclosed. The tag is characterised in that the or one of the magnetic materials on the tag is divided into distinct zones such that the zones and their relative positions can represent information or a code which is readable magnetically by passing the tag through a magnetic field which comprises a relatively small region of zero magnetic field (a magnetic null) contiguous with regions where the magnetic field is sufficient to saturate said magnetic material, the tag being moved through the magnetic field and its magnetic response being detected as it traverses the magnetic null.

Abstract: 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.