Abstract: A device monitoring and recording system is described which is particularly applicable to on-board vehicle monitoring and recording of operating engine parameters. The system comprises a plurality of sensors for sensing operating parameters of the engine and for generating data signals in response thereto, a data processing unit for receiving the data signals and a portable data link for extracting the processed data. Means are also provided for analyzing the processed data in remote computing means to provide printouts for record keeping, maintenance and diagnostic purposes.