1-20

(canceled)

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21

A signal analyser comprising: signal receiving means operable to receive a signal for analysis; signal processing means operable to process the received signal and identify the occurrence of any of a plurality of predetermined signal features; a classification engine operable to increment or decrement one or more individual belief index values in response to the identification of predetermined signal features, each individual belief index corresponding to one of a plurality of potential signal classifications; and means for providing an indication of the classification of the signal based on the individual belief index values.

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22

A signal analyser as claimed in Claim 21 wherein belief index values are incremented or decremented according to an algorithm or a look up table of increments and/or decrements corresponding to the feature or features identified in the signal.

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23

A signal analyser as claimed in Claim 21 wherein the increments or decrements are varied according to absolute or relative properties of the detected feature or features or wherein increments or decrements in response to a particular feature are applied to only one or to more than one belief index value and the increment or decrement need not be the same for each belief index value.

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24

A signal analyser as claimed in Claim 21 wherein the increments or decrements are filtered by a temporal window.

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25

A signal analyser as claimed in Claim 21 wherein belief index values are used to calculate belief index ratings and by considering the relative belief index rating of each potential signal classification an indication as to the overall signal classification can be obtained.

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26

A signal analyser as claimed in Claim 25 wherein the belief index ratings are calculated from the belief index values by use of a suitable function which rises relatively slowly at either end of the range of belief index values and relatively rapidly in the middle of the range of belief index values.

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27

A signal analyser as claimed in Claim 25 wherein the belief index ratings are provided to an operator in order that the operator may make a judgement as to the classification of the signal or wherein the analyser automatically classifies the signal, either if a particular belief index rating exceeds a predetermined classification threshold level or if two or more belief index ratings exceed the predetermined classification threshold level wherein the signal is assigned the classification of the highest belief rating or a joint classification.

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28

A signal analyser as claimed in Claim 27 wherein once a signal has been classified, it will retain the classification so long as the relevant belief index rating does not drop below a predetermined de-classification threshold level and so long as no other belief index rating exceeds the predetermined classification threshold level, the de-classification threshold level being lower than the classification threshold level.

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29

A signal analyser as claimed in Claim 25 wherein the analyser is operable to periodically sample the signal and update each belief index value and hence update each belief index rating and wherein the analyser is operable to increment or decrement each belief index at regular time intervals on the basis of features identified in the signal during a pre-selected number of previous time intervals.

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