Field of the Invention

This invention relates to an identification (ID) tag reader, system and method.

Background of the Invention

It is common to provide ID tags which are associated with assets, for example people or property. This allows the ID tag to be scanned or read by a reader and as a result for the status of the asset to be logged in a database, whether locally or remotely. The ID tag could for example be a swipe card or a radio frequency (RFID) tag associated with a person, and used in the workplace to indicate whether that person is in or out of the building.

Similarly, the ID tag could be associated with an item, for example a high-value tool or piece of machinery.

The ID tag could be associated with an intangible asset, such as a task or job.

Applicant has identified a need for an ID tag system that allows an affirmative transfer of the asset or asset responsibility from one 'owner' to another. The term 'responsibility' is meant in a broad sense and can simply refer to a temporary association between an owner and an asset. The owner can be any person or entity. An example is responsibility for high-value equipment which changes hands between different people (owners) over the course of a week. Current systems do not cater for this situation, at least not in an intuitive way. A first owner, for example, may assume they are still responsible for the equipment but a second owner may have subsequently scanned the asset's tag, thereby assuming responsibility themselves, without the first owner's knowledge. Ambiguity therefore results which can be a serious problem if the asset is lost or stolen.

Summary of the Invention

A first aspect of the Invention provides a tag reader for a system that uses multiple tag readers for reading tag ID data, the tag reader comprising: a memory for storing one or more tag IDs indicative of a responsibility held by said reader; a proximity sensor configured to identify the presence of another in -range tag reader with which to pair; a reading sensor configured to read a tag to determine at least part of its tag ID; and a processor configured to communicate with the paired reader to cooperatively identify which of the readers has current responsibility for that tag ID and to exchange responsibility between the readers.

The processor may be configured to generate a proposed transfer direction which it sends to the other reader, to receive a second proposed transfer direction from the other reader, and to exchange responsibility between the readers in that the event that said messages agree.

The processor may be arranged to write into memory details of each exchange, including the tag ID, direction of exchange and an ID associated with the other reader.

The processor may be further arranged to write into memory details of the date/time of said exchange.

The processor may be further arranged to communicate details of each exchange from its memory to a remote database or server.

The reading sensor and processor may be configured to operate automatically, responsive to the proximity sensor identifying the presence of the other reader. The processor may be arranged prior to reading the tag ID to enter a status setting mode to determine a master/slave relationship with the other reader, which relationship determines subsequent data communications between the readers.

The reading sensor may be optical, having a light emitter module for exposing light to the other reader through an encoding region of a tag which in use is located between the paired readers, and a light detecting module for detecting light from the other reader, the reader in use reading only part of the tag ID which is subsequently joined with the other part of the tag ID read by the other reader to generate the complete tag ID. The master/slave relationship may determine whether the reader transmits its part of the tag ID to the other reader or receives the other part of the tag ID from the other reader.

Data communications to and from the other reader may be by means of optical signalling. The tag reader may be arranged to mechanically engage with another reader with which it is to pair and comprising an engagement surface or structure arranged to temporarily engage with a corresponding engagement surface or structure of the other reader in a predetermined orientation.

The engagement surface or structure may comprise first and second complimentary-shaped parts arranged such that, when engaged, the paired readers will be in upside-down in relation to each other. One part of the engagement surface of structure may comprise one or more projections and the other part a corresponding number of recesses of similar shape.

The tag reader may be arranged such that when the tag reader is mechanically engaged with another reader, a recess or channel is defined between the engaged readers into which a tag is in use located for reading by both readers.

One or more tag attachment members may be provided on the engagement surface of the reader that, in use, hold the tag in position in relation to the reader. A second aspect provides an optical tag reader system for reading tags having a tag ID encoded thereon, the system comprising a plurality of tag readers which can be selectively connected together in a pairwise manner by means of respective engagement portions which, when connected, define between the readers a slot or recess into which an ID tag can in use be secured adjacent an optical sensor of each reader, each reader also having a light emitter which in use emits light towards the ID tag and the optical sensor of the other reader so that each reader is able to read part of the tag ID and subsequently exchanges information with the other so that both can identify the complete tag ID, wherein each reader uses the tag ID to identify from local memory which one of them is currently identified as being responsible for said tag and then exchanges responsibility with the other reader.

Another aspect provides an ID tag for use with a tag reader or tag reader system of any preceding definition. Another aspec t provides an IDtag foruse in an opticaltag readingsysteminwhich pairsof tagreaders emit lightthrough t heIDtag towardseachother to enable readingofa tagID, the ID tagcomprisinganencodingregionproviding a plurality of areaswhich encode the tagID in by meansofholes or blanks, and furthercompirsingone or more holesoutside of the 55 encoding region to permit opticaldatasignalling between the tag readers.

Another aspect provides a method of operating a tag reader, compirsing: storing one or more tag IDs indicative of an asset responsibility; sensing the presence of another in-range tag reader; reading the tag ID of an in-range tag; communicating with theother tagreaderto 10 cooperativelyidentifywhich of thetwo readershas currentresponsibility for that tagID; and exchanging responsibility between the readers. Another aspect provides a method of operating an optical tag reading system for tags having atag ID encoded thereon, the method comprising c on necting together in a pair wise manner

15 first and second tag readers by means of respective engagement portions which, when connected, define between the readers a slot or recess; locating an ID tag within the slot or recess with an encoding region of the tag adjacent a light emitter and optical sensor module of each reader; emitting light from each light emitter towards the ID tag and optical sensor of the other reader; using the optical sensor of each reader to read are spective part of the tag ID;

20 exchanging the partial tag ID information so that the readers both identify the complete tag ID; comparing the tag ID with local memory to determine which reader currently has responsibility for the tag ID; and exchanging responsibility for the tag ID between the two readers.

25 B rief Description of the Drawings

The invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:

Figures -c show, respectively, an ID tag according to the invention, and ID tag connector 30 and the ID tag when connected to an asset;

Figures 2a-b show opposite sides of the ID tag of Figure and a detailed view showing its encoding grid;

Figure 3 is a perspective view of an ID tag reader according to the invention; Figure 4 is a perspective view of the ID tag of Figure 1 inserted between two Figure 3 ID tag when connected in a pairwise manner in opposite orientation;

Figure 5 is a schematic view of an emitter/sensor portion of the ID tag reader;

Figure 6 is a schematic view representing emitter/sensor portions of two co-located ID tag readers, which is useful for understanding the invention;

Figure 7 is a block diagram showing functional components of an ID tag reader;

Figure 8 is a schematic view similar -to Figure 6 but which includes between the co-located

ID tag readers the ID tag encoding grid;

Figure 9 is a flow diagram indicating the processing stages performed by the ID readers; and Figure 10 is a flow diagram showing the main processing stages in a tag reading and communications phase between the ID readers.

Detailed D escription of Preferred Em bodiments

Embodiments herein relate to an ID tag reading system that is particularly suited to situations requiring the affirmative transfer of an asset or asset responsibility from one owner to another. An asset can be tangible or intangible, and the owner can be a person or other entity. Responsibility means some assignment or association between an asset and entity which is temporary. 1. Overview

The first embodiment is a system that provides multiple ID tag readers (hereafter "tag readers") each of which is associated with a respective person. The tag readers are portable and include a battery for powering internal components of the reader, which battery can be recharged or replaced as and when required. Typically, a person will wear the tag reader around their neck or attach it to their belt.

The tag readers are designed in use to mechanically connect together so that two can be temporarily paired, and when so paired, a channel or recess is defined in-between into which an ID tag can be secured ready for reading. The tag readers are configured such that mechanical pairing also causes a proximity sensor on each to electrically detect said pairing, causing internal electronics of each reader automatically to wake-up and enter into a series of operating stages which ultimately lead to both tag readers cooperatively reading the ID tag, checking their own memory database to identify which has current responsibility for this ID tag, and then under certain conditions causing an affirmative transfer of responsibility from the current tag reader to the other, with the former releasing responsibility.

Confirmation of the transfer is visually and/or audibly output, and the paired readers can then be mechanically parted in the knowledge that transfer has occurred.

Each tag reader stores on local memory the tag ID of tag(s) it is currently responsi may also store data indicating the other tag reader involved in transaction(s) and th d time of the transaction. Errors, such as a non-verification situation, can also be logged.

A central database or server can at the same time, or at a later time, update its own records to reflect transactions performed by the tag readers. This provides a current and historical picture of which owners have or had responsibility for which assets and, in the event of an issue with a tagged asset, there is an affirmative record of who accepted responsibility for that asset and when.

The ID tap themselves can be of any form but in the present case comprise punch-hole type tags with the readers employing optical means to identify and read the tap. 2. ID Tag

Figure la shows an example ID tag 10 for use in the present embodiment. The ID tag 10 comprises an elongate planar strap of plastics or similar material, having a narrow 'neck' portion 12 and a wider 'head' portion 14 into which is encoded the tag's unique ID number by means of a particular arrangement of holes/blanks on a grid 16.

Two outer columns 17 of holes, either side of the encoding grid 16, are used for mechanical support and alignment of the ID tag 10 relative to a card reader, which will be described later.

The neck portion 12 comprises two columns of holes 18 which can be engaged at any point along the neck by correspondingly-arranged pegs of a two-piece connector system 20, shown in Figure lb, which fit either side of the neck. A cover portion 21 locates over this two-piece connector 20 and is used to secure the ID tag 10 to an asset, e.g. a laptop 22, as shown in Figure 1c. It will be seen that the ED tag 10 can be used by lifting the head portion 14 away from the asset 22 at which point a pair of tag readers are able to read said tag in the manner to be explained below. Otherwise, the ID tag 10 is fairly discreet when located against the asset 22.

Figure 2 shows in close-up the ID tag's encoding grid 16 introduced previously. Figure 2a shows the ID tag 10 and grid 16 from one side, and Figure 2b from the opposite side when flipped over in the manner shown. Labels A and B are used to conveniently indicate the different sides. Column numbers and row letters are provided for easy reference to individual areas (or 'channels').

A subset of the grid 16 is used for encoding the ID tag's unique numerical ID; this subset is comprised of those twenty eight circular areas 30 without interior shading. Encoding is by means of the areas either being open (holes) or closed (blanks). A hole may signify a "1" and a blank a "0" or vice versa. We will assume the former. Thus, 2 ²⁸ possible combinations are possible for the numerical ID.

In addition, there are four 'special' areas 31, 32, 34, 46 at the corners and indicated as circles with interior shading. One area 31 at position W7 is always closed and is used for orientation, as will be explained later. Of the other areas:

W0 corresponds to the Master Clock Channel 32;

Z0 corresponds to the Master Transmission / Slave Receiving Channel 34; and

Z8 corresponds to the Master Receiving / Slave Transmission Channel 36.

These three areas 32, 34, 46 are always open. 3. Tag Readers

Referring to Figure 3, a tag reader 40 is shown. The tag reader 40 comprises a container-like unit having a front part 42 connected to a rear part 44 by means of a peripheral wall defining between the two parts an interior space into which the battery and electronic circuitry (not shown) are fixed on a circuit board. A flange 46 projects from an upper wall thereof and has a hole to enable the tag reader 40 to be clipped to a user's belt or to a chain or band which goes around the user's neck. On the front part 42 is arranged a series of recesses and projections 48, 50 arranged in two portions for the purpose of allowing the tag reader 40 to mechanically engage with another tag reader in upside-down orientation. This engagement is shown in Figure 4 with said reader engaged to a second reader 80 which is upside down and mounted on the front. The ID, tag 10 is shown in position in-between the two readers 40, 80.

Returning to Figure 3, on the upper portion of the front part 42 are arranged two pairs o recesses 48 of circular cross-section. On the lower portion of the front part 42 are arranged two pairs of three projecting pegs 50 which are correspondingly-shaped and have a cross- sectional diameter slightly smaller than each recess 48. The length of the pegs 50 is slightly greater than the depth of die recesses 48 so that, when two such readers 40, 80 are engaged as shown in Figure 4, there is a small gap between the two adjacent front parts 42 within which the ID tag 10 can locate. Alternative mechanical connectors can be used to achieve the same purpose.

On the front part 42 between these mechanical engagement members 48, 50 are arranged apertures for emitters and sensors provided on an exposed side of the internal circuit board (not shown); the emitters and sensors are utilised for the actual reading of the ID tag 10 and for data communications through the special channel holes mentioned above. The upper set of apertures 54 exposes a grid-like arrangement of sixteen light sensors (4x4) on the circuit board, whereas the lower set of apertures 52 exposes a grid-like arrangement of four light emitters (e.g. LEDs) (2x2) on the circuit board. When the ID readers 40, 80 are engaged as in Figure 4, it will be appreciated that the lower set of apertures 52 on one reader will be co- located with the upper set of apertures 54 on the other , and vice versa.

In locating the TD tag 10 between the two tag readers 40, 80 the outer columns 17 of holes are arranged to locate over the pegs 50 of each reader; this secures the ID tag securely in aligned position between the mechanical pairing such that the encoding grid 16 is positioned correctly with respect to the LEDs and sensors. Each area of the encoding grid is adjacent a corresponding sensor on one reader and an LED on the other.

At this stage, it will be evident that reading of an ID tag 10 is by means of detecting the presence or absence of light, emitted from the LED of the opposing reader, at a light sensor. A hole in the encoding grid will result in a ' l' and a blank will result in a '0' using the assumed convention. Identification of the ID tag's unique code requires a reading of each of the tag's areas. However, it will also be evident from the Figure 4 configuration, that each tag reader 40, 80 can only directly 'read' a subset, or half, of the ID tag's encoding grid 16. Therefore, each tag reader 40, 80 is arranged to read half of the encoding grid 16 and one or both of the readers passes this information to the other during the read process, as will be explained below. This data transfer occurs using one of the special channels 6 mentioned above. Referring to Figure 5, the PCB 60 of the tag reader 40 is represented here showing the arrangement of 2x2 LEDs 62 and 4x4 light sensors 64 which are on the exposed side. Each element is indicated by a row and column reference for ease of explanation later on.

Figure 6 shows the relative positions of two PCBs 60, 90 when two such tag readers 40, 80 are connected in the manner shown in Figure 4. Regarding the nearest PCB 90 of tag reader 80, note that the LEDs 63 and light sensors 64 are directed towards the other PCB 60 (into the page) rather than as shown. The ID tag 10 will be operatively located between the two PCBs 60, 90. It will also be evident that in order to minimise components and circuitry, each LED 62 is associated with four sensors 64 of the opposite tag reader. This requires a specific sector-wise sequence of LED illumination, as will be explained.

Figure 7 shows the hardware functional modules 61 of each tag reader 40, 80. These are provided on the circuit board and include the aforementioned LED array 62 and light sensors 64, specifically a photo-transistor (PT) array 64. Each is connected to a microcontroller 65 that controls operation of the various components under software or firmware control. Also connected to the microcontroller 65 is a set of set of status indicators 78, non-volatile memory 76 for storage, a regulator 68, a sensor power controller 70 and a system power controller 74. A battery cell 66 is connected to the regulator 68 and to a reed switch 72 (having an associated magnet 73). A key indicates the various signal types, i.e. power, analogue and digital signals.

The microcontroller 65 can be a single controller or plural controllers, or a microprocessor or plural microprocessors. The reed switch 72 acts as a proximity detector, and is arranged on the circuit board of the tag reader 40, 80 such that when two readers are co-operatively connected as in Figure 4, the associated magnet 73 of one reader closes the other reader's reed switch. The purpose of the proximity detector will become clear.

The operation of the tag readers 40, 80 will now be described when an ID tag 10 is correctly positioned between a pair of readers in the manner shown in Figure 4. This is the operation that will be applied in a typical handover between respective owners in relation to an asset associated with the ID tag 10.

Figure 8 shows the aforementioned PCBs located either side of encoding grid 16 of an ID tag 10, which may be useful in understanding the operation. Regarding the nearest PCB 90 of tag reader 80, the LEDs 63 and light sensors 64 are directed towards the other PCB 60 (into the page) rather than out of the page as shown.

In overview, and with reference to Figure 9, the following operating stages occur in order.

1. Transaction Initiation Phase - both tag readers 40, 80.

2. Device Detection and Threshold Calculation Phase - both tag readers 40, 80.

3. Orientation and Role Assignment Phase - both tag readers 40, 80.

4. Synchronisation Phase - each tag reader 40, 80 assumes a different role.

5. Communication Phase - each tag reader 40, 80 assumes a different role.

6. Result Indication Phase—both tag readers 40,, 80.

7. Power Save Mode - both tag readers 40, 80.

1. Transaction Initiation Phase - both tag readers 40. 80.

1.1 Magnets 73 of one tag reader activate the opposing tag reader's reed switch 72 (reed switches are activated by opposing devices magnets).

1.2 The reed switch 72 routes a signal from the battery 66 to the System Power Controller 74, indicating transaction initiation.

1.3 The System Power Controller 74 routes a DC signal from the battery 66 through a high pass filter to the regulator 68 which activates the regulated system power for a short period of time. This is the primary regulator-enable signal. 1.4 The Microcontroller 65 powers-up and immediately provides a secondary signal to enable the regulator 68. After a short period of time this signal will become the only signal responsible for enabling the regulator 68 (once die primary signal has diminished through the filter).

1.5 The reed switch 72 routes a signal from the battery 66 to the Sensor Power Controller 70 which in turn activates power to the photo-transistor array 64.

1.6 Go into next phase.

2. Device Detection and Threshold Calculation Phase - both tag readers 40, 80.

2.1 In a mutually exclusive fashion, continuously alternate LED's L2 and L4 of LED array 62 with a fixed frequency Fl and a 50% duty cycle. This allows the tag readers 40, 80 to detect each other and determine appropriate threshold levels for communication.

2.2 Sample sensors AO and DO of the photo-transistor array 64 over a period which is four times greater than the period of Fl . Take the average value over this period for each sensor

2.3 Use these values as an initial threshold for decimation. Continue to sample and, using this decimation threshold, look for a square wave on each sensor.

2.4 Once a square wave is found, find a suitable high level (logic ' 1 ') in the signal and use it to determine a more accurate decimation threshold.

2.5 Any calculated thresholds which fall below a minimum value are set to maximum value so that after decimation only low levels (logic Ό') are found.

2.6 Repeat until at least one sensor finds a square wave or until a timeout occurs.

2.7 Go into next phase. 3. Orientation and Role Assignment Phase - both tag readers 40. 80.

3.1 As before, in a mutually exclusive fashion, continuously alternate LED's L2 and L4 with a fixed frequency F l and with a 50% duty cycle.

3.2 Count square wave cycles on sensors AO and DO using the previously-defined decimation thresholds.

3.3 Look for a defined minimum number of cycles on either channel AO, DO.

3.4 If the same number of cycles is found on both channels AO, DO, the role of the device is a slave since it has access to a clock and data signal. The slave device now uses the master device clock signal for communications rather than its own internal timers. 3.5 If a minimum number of cycles are found on one channel but no cycles are found on the other, the device performs a master role since it only has access to a data signal and no clock signal.

3.6 Go into next phase.

In the case of Figure 8, note that sensor AO of ID reader 40 will not receive the same number of cycles as sensor DO due to area 31 at D7 on the ID tag 10. Accordingly, ID reader 40 is the master device and ID reader 80 the slave. 4. Synchronisation Phase - each tag reader 40. 80 assumes a different role- Master Device

4.1.1 As before, in a mutually exclusive fashion, continuously alternate LED's L2 and L4 with a frequency Fl and with a 50% duty cycle.

4.1.2 Look for reduced frequency in the signal sent by the slave device. Once found, (his confirms that the slave is also in the synchronisation phase.

4.1.3 Stop flashing the LED corresponding to the Master-Tx tag channel. This indicates the start of the synchronisation to the slave device.

4.1.4 The master device knows that synchronisation will occur on the next clock cycle.

4.1.5 Go into next phase.

Slave Device:

4.2.1 As before, in a mutually exclusive fashion, continuously alternate LED's L2 and L4 but this time with a reduced frequency F1 / 6.

4.2.2 Look for one of the master device square wave signals to stop. This indicates the start of the synchronisation and also tells the slave device which sensor is used for the clock signal and which is used for data.

4.2.3 The master and slave devices are now fully synchronized to the master clock and will both start exchanging data on the next master clock cycle.

4.2.4 Go into next phase .

5. Communication Phase - each tag reader 40, 80 assumes a different role .

Master Device:

5.1.1. Send command ID to slave device indicating a tag transfer is about to commence. 5.1.2. Read tag channels X7, X6 and W6 while the slave illuminates those channels.

5.1.3. Read tag channels Y7, Y6 and Z6 while the slave illuminates those channels.

5.1.4- Read tag channels X5, X4, W5 and W4 while the slave illuminates those channels. 5.1.5. Read tag channels Y5, Y4, Z5 and Z4 while the slave illuminates those channels. 5.1.6. Exclusively illuminate the LED corresponding to tag channels X0, X 1 and Wl .

5.1.7. Receive the read sensor values from the slave device.

5.1.8. Exclusively illuminate the LED corresponding to tag channels YO, Y1 and Z1.

5.1.9. Receive the read sensor values from the slave device.

5.1.10. Exclusively illuminate the LED corresponding to tag channels X5, X4, W5 and W4. 5.1.11. Receive the read sensor values from the slave device.

5.1.12. Exclusively illuminate the LED corresponding to tag channels Y5, Y4, Z5 and Z4.

5.1.13. Receive the read sensor values from the slave device.

5.1.14. Determine the tag ID.

5.1.15. Send the master device ID to the slave device.

5.1.16. Receive the slave device ID.

5.1.17. Send the tag ID value to the slave device.

5.1.18. Determine the direction of the tag transfer. If the tag ED exists in the master device database then the tags direction is towards the slave away from the master, otherwise it's towards the master away from the slave.

5.1.19. Process the transaction details to confirm that the details are valid and that the transaction is authorised.

5.1.20. Send the transaction direction to the slave device.

5.1.21. Receive the transaction direction from the slave device.

5.1.22. Check that the master and slave direction values agree.

5.1.23. Send the result of that check to the slave.

5.1.24. Receive the result of the slave device direction check.

5:1.25. If both master and slave devices agree to the transaction, the transaction details are committed to the database.

5.1.26. Any failed transactions are also recorded in the database along with the error code. 5.1.27. Go into next phase.

Slave Device:

5.2.1 Read tag transfer command from master device.

5.2.2 Exclusively illuminate the LED corresponding to tag channels X7, X6 and W6. 5.2.3 Exclusively illuminate the LED corresponding to tag channels Y7, Y6 and Z6.

5.2.4 Exclusively illuminate the LED corresponding to tag channels X5, X4, W5 and W4.

5.2.5 Exclusively illuminate the LED corresponding to tag channels Y5, Y4, Z5 and Z4.

5.2.6 Read tag channels X7, X6 and W6 while the master illuminates those channels.

5.2.7 Send the read sensor values to the master device.

5.2.8 Read tag channels Y7, Y6 and Z6 while the master illuminates those channels.

5.2.9 Send the read sensor values to the master device.

5.2.10 Read tag channels X5, X4, W5 and W4 while the master illuminates those channels.

5.2.11 Send the read sensor values to the master device.

5.2.12 Read tag channels Y5, Y4, Z5 and Z4 while the master illuminates those channels.

5.2.13 Send the read sensor values to the master device.

5.2.14 Receive the master device ID.

5.2.15 Send the slave device ID.

5.2.16 Receive the tag LD.

5.2.17 Determine the direction of the tag transfer. If the tag ID exists in the slave device database then the tags direction is towards the master away from the slave, otherwise it's towards the slave away from the master.

5.2.18 Process the transaction details to confirm that the details are valid and that the transaction is authorised.

5.2.19 Receive the transaction direction from the master device.

5.2.20 Send the transaction direction to the master device.

5.2.21 Check that the master and slave direction values agree.

5.2.22 Receive the result of the master device direction check.

5.2.23 Send the result of that check to the master.

5.2.24 If both master and slave devices agree to the transaction, the transaction details are committed to the database.

5.2.25 Any failed transactions are also recorded in the database along with the error code.

5.2.26 Go into next phase.

6. Result Indication Phase - both tag readers 40. 80.

6.1 Results are indicated to the user by way of 2 LED indicators of status indicator 78; one red and one green.

6.2 Results are displayed for 10 seconds following any transaction attempt.

6.3 Flashing green indicates that a reader has successfully released a tag. 6.4 Solid green indicates that a reader has successfully acquired a tag.

6.5 Flashing red indicates that a transaction has failed.

6.6 Solid red indicates a low battery.

6.7 Alternating red and green indicates a device malfunction.

6.8 Go into next phase.

7. Power Save Mode - both tag readers 40. 80.

7.1 If device settings dictate; completely shut down the reader after a transaction. The next transaction will switch the device back on.

7.2 If device settings dictate; go into low power mode after a transaction, keeping timers alive. The next transaction will wake the device from its low power state.

It will be appreciated that certain ones of the above stages and individual steps can be omitted or re-ordered.

For completeness, an abbreviated overview of the communications phase is shown in Figure 10, which is self-explanatory and shows the key stages. The channel segments referred to indicate segments illuminated by each LED of the other reader 40, 80 with the grid references given previously.

In summary, there has been described a reader system and constituent readers which are arranged to work cooperatively in selective pairs to enable assets effectively to be re-assigned between readers (or, in practise, entities associated with readers) in a straightforward and intuitive manner enabling both a local and global picture of asset responsibility to be reliably gathered. The global picture can be updated wirelessly, if each reader were for example to include a wireless communications module, such as Bluetooth. Alternatively, or additionally, the readers could upload their memory contents through a wired connection to a computer terminal. The design of the tag for use with such readers is also considered intuitive, particularly the provision of an orientation element to establish a master/slave relationship, and the provision of a plurality of holes not forming part of the encoding grid 16 enabling bidirectional data communications between the paired readers using optical signals. A master clock signal can also be transferred across the tag in the same way. It will be appreciated that the above described embodiments are purely illustrative and are not limiting on the scope of the invention. Other variations and modifications-will be apparent to persons skilled in the art upon reading the present application.

Moreover, the disclosure of the present application should be understood to include any novel features or any novel combination of features either explicitly or implicitly disclosed herein or any generalization thereof and during the prosecution of the present application or of any application derived therefrom, new claims may be formulated to cover any such features and/or combination of such features.