UNIX time-sharing system: No. 4 ESS diagnostic environment

Maintenance and testing of the Voiceband Interface and the Echo Suppressor Terminal in No. 4 ESS are aided by software in the 1A processor. A No. 4 ESS diagnostic environment was needed during the development phase of both the hardware and diagnostic software. The minicomputer chosen to support this environment was also required to support the development of more than one frame at the same time. Because of this requirement and other reasons, the UNIX∗ operating system was selected for software support and development. This paper describes how the UNIX operating system was applied to this project.