Abstract: In the present invention signals are obtained from a plurality of sensors S1, S2, Sn and fed into an encoder (12). The encoder (12) is operable in use to receive input signals from each of the sensors S1, S2, Sn and translate said signals into one or more vectors characterising the state of one or more of the operational parameters of the monitored system, hereinafter referred to as an encoded vector VE. The signals from the sensors S1, S2, Sn may relate to one or more different operational parameters of a connected system. The encoded vector VE is fed into a translation engine 13 which translates the encoded vector VE into feature space to form a feature vector VF.