De La Rue International Limited

Peter Alan Pullan

John Alan Skinner

Michael Potter

Peter Dilwyn Evans

John Buttifant

Barry Clifford Scowen

A method of detecting a coded magnetic thread is provided that includes sensing the response of a magnetic field detector as a thread passes the detector, the response varying from an initial magnitude in first and second senses to exhibit a first peak, and then in the first sense to exhibit a second peak; comparing the response with first and second thresholds disposed about the initial magnitude in the first and second senses respectively; and indicating the passage of a code element of the thread when the response passes the second threshold and then the first threshold in a predetermined manner characterized in that the first threshold is adjusted in accordance with a first predetermined algorithm based on the magnitude of the first peak. The first predetermined algorithm adjusts the first threshold so that the magnitude of the first threshold is the average of a predetermined number of preceding first peaks.

Apparatus for and method of detecting a coded magnetic thread

Systems and methods for identifying a coded magnetic thread comprise generating a digital representation of the thread and comparing the digital representation with one or more known digital representations; scanning the digital representation to locate a predetermined code sequence; and rotating the digital representation to locate the predetermined code sequence in a predetermined position corresponding to the position of the predetermined code sequence in a stored version of the or each known digital representation prior to carrying out the comparison.

Magnetic thread reader

A method of detecting a magnetic thread comprises causing relative movement between the thread and an array of magnetic heads, each head generates a signal upon detecting a portion of the thread. The arrival of a thread at one of the heads is detected, that head being denoted a primary head, and the head on each side a secondary head. Output signals from the primary and secondary heads are monitored to generate a representation of the thread, and the magnitude of the signals from the primary and secondary heads are compared such that if the magnitude of the output signal from a secondary head exceeds that from the primary head, the primary and secondary heads are reallocated accordingly.

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Hampshire, United Kingdom

Peter Alan Pullan