Abstract: An expert system having a processor which can receive input data and operate on it to produce data indicative of a parameter or parameters which are considered to define or represent the condition of equipment or a system to be diagnosed and which provides an adaptive pattern recognition facility which can be trained or instructed to recognize different combinations of input data as indicative of particular conditions of the equipment. The system is trained by coupling it initially to known good equipment into which definable faults are introduced. The adaptive pattern recognition facility has a series of sections with adjustable weight coefficients which are adjusted in accordance with a given algorithm as successive data combinations associated with the various faults are fed to the system. Once trained, the system can diagnose unknown equipment and provide outputs indicative of faults.

Abstract: A digital filter comprises a plurality of delay stages 41 such as shift register stages through which an input x(t) is fed. Each of a plurality of individually addressable random access memories 42 is addressed by the output of one of the delay stages and the output from the RAMs 42 are combined. An error signal adapts the values stored within the RAMs. The filter may also be extended such that each RAM receives an address input from more than one delay stage.