Such systems are well known and include sorters, counters, dispensers, acceptors and recirculators. An important function performed by such systems is to check the identity of a document, for confirming the document has an expected identity or in order to identify the document so that it can be sorted or counted.

Typical techniques for determining the identity of documents include size and pattern recognition techniques.

In the case of bank notes, where different denominations of bank note have different sizes as is common in many countries, a measure of the document size can be used directly to determine denomination. In other countries, more than one denomination has the same size, and a different technique such as pattern recognition or possibly magnetic thread reading is used to determine denomination.

In typical identity determining systems, a processor is located within the system which can determine the identity of a document by processing information obtained from the document and utilising data from a memory corresponding to known document identities. This data is commonly supplied on an EPROM. When it is desired to change the data, for example because of changes in currency patterns and the like, a new EPROM is supplied to the customer which he can then fit in place of the previous EPROM.

A problem with this is that the EPROMs are relatively easy to copy and there is a need to prevent an EPROM supplied to one customer for use on one machine being used on other machines without satisfactory payment to the supplier.

In accordance with the present invention, a document identity system comprises a document reading device for obtaining information about a document; a memory for storing data relating to documents to be identified; and a processor for determining the identity of a document by processing the information and data in a predetermined manner and is characterised in that the document reading device has a store for storing a unique identifier relating to the device; and in that the memory is a detachable read- only memory which also stores one or more identifiers, the processor only carrying out the document identity determination process if the unique identifier in the store matches the or one of the identifiers in the memory.

In this invention, the memory is made system specific so that it can only be used with those reading devices for which it stores a corresponding unique identifier. Thus, if the memory is fitted to a reading device for which it does not have a corresponding unique identifier or a copy of the memory is made and fitted to such a reading device, the two would not work together.

Typically, the memory is an EPROM or EEPROM although other types of memory could also be used.

To reduce the possibility of the or each identifier being illicitly read from the memory, the identifier is preferably embedded in the memory. In other words it is hidden in such a way as to make it hard to locate when using reverse engineering methods.

Similarly, preferably the store has the unique identifier embedded within it and conveniently the store comprises an integrated circuit device.

Typically, the store has a data structure which makes it incompatible for use with other reading devices.

The data relating to documents to be identified will typically comprise size and/or pattern data as is known in the art.

To increase security still further, preferably the or each identifier in the read-only memory is encrypted, the

processor being adapted to decrypt the identifier to determine the match.

For even further security, software used by the processor to determine a match may be embedded in a program memory. This makes it very difficult for the program to be read in an unauthorised manner.

In order that the memory is not changed during operation of the system, preferably the processor is adapted regularly to request an identifier from the memory and to. carry out the matching process.

Although the invention is particularly suited for use with reading devices in which the documents are transported past the reading device, it could also be applied to systems in which the document remains stationary, for example is manually introduced to the reading device.

An example of a document identity determining system according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a cross-section through the system; and, Figure 2 is a block diagram of the control arrangement of the system shown in Figure 1.

The present invention is typically implemented in a counter as shown in Figure 1. As shown, the counter includes an input hopper 2 mounted beneath an inlet opening 3 in an enclosure 1 which comprises upper and lower parts la, 1b normally screwed together. Contained within the enclosure 1 is an internal chassis assembly (not shown for clarity) which itself has side members between which the sheet feeding and transport components to be described herein, are mounted. Two conventional feed wheels 5 are non-rotatably mounted on a shaft 7, which is rotatably mounted to the chassis assembly, and have radially outwardly projecting bosses 6 which, as the feed wheels rotate, periodically protrude through slots in the base of the hopper 2.

A pair of stripper wheels 15 are non-rotatably mounted on a drive shaft 16 which is rotatably mounted in the

chassis assembly. Each stripper wheel 15 has an insert 17 of rubber in its peripheral surface. Shaft 16 is driven clockwise by a motor 200 (Figure 2) to feed banknotes individually from the bottom of a stack of banknotes placed in the hopper 2.

Transversely in alignment with, and driven from the circumferential peripheral surface of the stripper wheels 15, are pressure rollers 30 which are rotatably mounted on shafts 31 spring biased towards the stripper wheels 15.

Downstream of the wheels 15 is a pair of transport rollers 19 non-rotatably mounted on a shaft 20 rotatably mounted in the chassis assembly. Shaft 20 is driven clockwise from a second motor 210 (Figure 2) to transport the banknotes in the transport arrangement, in conjunction with pairs of pinch rollers 21 and double detector rollers 23, into stacking wheels 27 and hence output hopper 95. Pinch rollers 21, rotatably mounted on shafts 22 spring biased towards the transport rollers 19, transversely align with rollers 19 and are driven by the peripheral surface of the rollers 19. The double detector rollers 23, rotatably mounted on shafts 24 are in alignment with the transport rollers 19, and are essentially caused to rotate by the banknote passing between the adjacent peripheral surfaces of the rollers 19 and 23.

Situated between the pressure rollers 30 and pinch rollers 21 are separator roller pair 25, non-rotatably mounted on shaft 26 adjustably fixed to a top moulding assembly 32, having a circumferential peripheral surface which is nominally in alignment with the peripheral circumferential surface of, but transversely separated from, the stripper wheels 15.

Also forming part of the top moulding assembly 32, is a curved guide surface 8 extending partly around the circumference of the rollers 15,19 which, when the top moulding is lifted allows the operator access to the banknote feed and transport path so that a banknote jam can be cleared. A surface 37 provides banknote guiding from

the end of the curved guide surface 8 to the conventional stacking wheels 27.

The drive motor 200 continuously drives the drive shaft 16, and, via a belt and pulley arrangement from shaft 16, the auxiliary drive shaft 7 rotating the feed wheel 5.

Drive shaft 20, rotating the transport rollers 19, is driven by the other drive motor 210. A further pulley and belt arrangement (not shown) between shaft 20 and shaft 28, on which the stacking wheels 27 are non-rotatably mounted, provides the drive to the stacking wheels 27.

A guide plate 9 extends as a continuation of the base of the hopper 2 towards the nips formed between the transport rollers 19 and the double detector rollers 23.

A linear detector array 50 is mounted adjacent to the transport path. This extends across the full length of the banknotes (transverse to the feed direction), so as to detect light reflected off the facing surface of banknotes as they pass beneath the detector. (Other known detectors could be used which, for example, only scan a portion or portions of the banknotes. Also, one or more detectors may be provided for determining transmittance, thickness, size, magnetic properties etc. of the banknotes.) The array 50 is coupled to a processor 220 via an analogue to digital convertor (ADC) 225 which samples the array 50 to obtain data relating to the reflectance properties of the banknote.

Typically, signals from the double detect rollers 23 will also be transferred to the microprocessor 220.

Accordingly, in use, banknotes entered into the input hopper 2 are transported along the transport path. The banknotes pass the detector array 50, which transfers reflectance signals to the processor 220 which operates to determine the denomination and authenticity of the banknotes in question. The banknotes then pass through the double detect rollers 23 and enter the stacking wheels 27 and hence the output hopper 105.

The transfer of the banknotes to the output hopper 105 can be controlled by the processor 20 in accordance with the detected denomination of the note. Alternatively the denomination indication can be used to calculate the value of the banknotes which are transferred to the output hopper 105, as will be appreciated by a person skilled in the art.

The manner in which the denomination of the bank notes is determined can take any conventional form but will typically comprise a pattern recognition technique, for example using a neural network or the like. Alternatively, a conventional pattern recognition system may be used.

Examples are described in more detail in WO-A-00/26861 incorporated herein by reference.

Pattern related information is supplied on an EEPROM 240 which can be removably attached to the processor 220.

As explained above, in order to limit the use of the EEPROM 240 to this particular reading device, the EEPROM 240 also includes a unique identifier or key, indicated at 245, which is embedded within it in an encrypted form.

The processor 220 is also permanently connected to an integrated circuit device 230 which includes a unique identifier or key, indicated at 235, which has been laser cut into the IC device and is unique to the machine and processor. Finally, the processor 220 is coupled to a ROM 250 in which is embedded software to enable the keys 235,245 in the stores 230,240 to be verified.

In use, when the system is activated, the processor 220 will extract the embedded key 245 from the EEPROM 240, decrypt it using the software from the store 250 and compare the decrypted key with the key 235 embedded in the IC device 230. If the comparison is successful, the processor 220 will then allow a document identity process to commence and will use pattern information in the EEPROM 240. At certain times, for instance, every time the transport starts to run, or every time the machine is powered on, the processor 220 will interrogate the EEPROM 240 to retrieve the encrypted key 245 and carry out the

comparison again. This ensures that no attempt has been made to replace the EEPROM 240 following an initial validation.

Typically, the EEPROM 240 will include a set of unique identifiers or keys corresponding to a group of bank note processing machines, for example all those belonging to a particular customer.