Abstract: A system for monitoring a machine (10) comprises a number of strategically placed sensing devices (11, 12, 13, 14) which are arranged to detect particular physical characteristics, such as vibration, thermal energy etc. Output signals from the sensing devices are delivered to a processor (15) which combines them to produce control signals indicative of the condition of a particular part or parts of the machine. In this way, the health of the machine can be continously monitored.