GB2201725A

GB2201725A - Security system

Info

Publication number: GB2201725A
Application number: GB08802604A
Authority: GB
Inventors: Neil James Hunter
Original assignee: Instrumentation & Microelectro
Current assignee: Instrumentation & Microelectro
Priority date: 1987-02-28
Filing date: 1988-02-05
Publication date: 1988-09-07
Also published as: GB8802604D0; GB8704765D0

Abstract

A key comprises a non-magnetic housing (12) containing a plurality of magnets (14) in a defined geometrical layout. The magnets (14) are arranged with north and south faces forming a predetermined code. In use, the key (10) is presented to a non-magnetic plate (16) covering a matching array of Hall-effect sensors (18), which each produce an output in response to the presence of a north or south pole, the outputs being fed to a logic device which produces an 'enable' signal on receipt of a correct set of outputs from the sensors. <IMAGE>

Description

Security System This invention relates to a security system comprising a coded key which can be carried by a user, and a detector activated by proximity of an appropriately coded key to provide an output.

Systems of this type are known and in use, but hitherto have suffered from complexity and high cost. It is known for example to use a key in which is encapsulated a miniature transmitter which is interrogated by radio frequency energy or by a low frequency inductive field, and to use magnetic stripes carrying a magnetic code.

An object of the present invention is to provide a security system which is simple and of low cost.

Accordingly the present invention provides a security system comprising a coded key and a detector device, the key being in the form of a portable nonmagnetic housing containing a plurality of magnets arranged at predetermined locations within the housing and having their north or south poles facing a front surface of the housing to define a predetermined code, the detector device comprising a non-magnetic plate to one surface of which the key may be applied and a plurality of detectors positioned adjacent the opposite surface of said plate in a predetermined pattern, each said detector being adapted to produce an electrical output modified by the adjacent presence of a magnetic field.

Preferably each detector is a Hall-effect device, most suitably one with a linear output.

The magnets are preferably ceramic magnets.

The number of detectors may equal the number of magnets, the detectors and magnets being arranged on matching grids. Alternatively the magnets may be arranged in a matrix and the detectors in a column, the key in use being moved in the row direction past the detectors.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig 1 is a schematic perspective view of a key forming part of the system of the present invention; Fig 2 is a schematic side view of the key of Fig 1 in proximity to a detector device; Fig 3 is an exploded perspective view showing a practical form of the key in greater detail; and Fig 4 is a schematic block diagram of the detector and related items.

The key 10 comprises a non-magnetic housing 12 in which are arranged in an array, a plurality of ceramic magnets 14. The magnets 14 are arranged with north or south poles facing the front surface of the housing 12 to define a code.

The detecting device comprises a non-magnetic plate 16 behind which are arranged a plurality of linear Halleffect devices 18 arranged in a matching array. When the key 10 is positioned against the plate 16, or in proximity thereto, each detector 18 produces an output indicative of whether a north or a south pole is adjacent to it. These outputs may be fed into a microprocessor or other logic device (not shown) to produce an enable output if a predetermined code is present.

In a modification, the key of Fig 1 may be used in conjunction with a detector device comprising a column of five detectors, the key 10 being "wiped" sideways across the column of detectors.

The plate 16 may suitably be provided with location means or guide means to ensure that the key is positioned against or moved across the plate in a correct position.

Figs 3 and 4 illustrate a practical form of the foregoing embodiment in greater detail. The housing 12 comprises a moulded plastics base 20 and cover 22 which click-fit together. The base 20 is formed with a plurality of recesses 24 each dimensioned to receive a corresponding ceramic magnet 14. The housing 12 is formed with an angled corner to ensure presentation in the correct orientation into a similarly-shaped recess 28 in plate 16 (Fig 4).

The base 20 mounts a ring 34 to allow the key 10 to act also as a holder for conventional keys.

The static part of the system (Fig 4) comprises the plate 16 and associated detectors 18, a control unit 30, a solenoid door latch 32 of known type; and a power supply unit 36.

The user can set his own code by inserting the magnets 14 in the recesses 24 in a desired pattern of north and south poles forward, and setting the same pattern in the control unit 30; for example, the control unit 30 may have a corresponding matrix of 2-position switches.

Other modifications may be made within the scope of the invention. For example the magnets could be arranged within a housing in a predetermined irregular pattern.

Any suitable number of magnets may be used to achieve the level of coding necessary for a desired degree of security.

Claims

1. A security system comprising a coded key and a detector device; the key being in the form of a portable non-magnetic housing containing a plurality of magnets arranged at predetermined locations within the housing and having their north or south poles facing a front surface of the housing to define a predetermined code, the detector device comprising a non-magnetic plate to one surface of which the key may be applied and a plurality of detectors positioned adjacent the opposite surface of said plate in a predetermined pattern; each said detector being adapted to produce an electrical output modified by the adjacent presence of a magnetic field.

2. The system of claim 1, in which each detector is a Hall-effect device

3. The system of claim 2, in which the Hall-effect devices are linear devices.

4. The system of claim 1, in which the magnets are ceramic magnets.

5. The system of claim 1, in which the magnets and detectors are equal in number and are arranged on matching grids.

6. The system of claim 5, in which the housing is of a non-symmetrical shape and the plate is provided with guide means for receiving said shape in correct alignment with the detectors.

7. The system of claim 1, in which the magnets are arranged in a matrix and the detectors in a column, the key in use being moved in the row direction past the detectors.