In 1961 a new engine laboratory was built. The long-term beds were built with open-loop automatic control and output systems. In 1968 the function test beds were fitted with automatic reading, output, and diagram drawing systems. In 1970 the next generation of long-term test beds was built.This paper presents a brief description of the various systems. The main emphasis is on the units which have reduced dependability and the successful actions later taken to restore this dependability to an acceptable level.