Comprehensive maintenance software is required to meet the system reliability objective of less than an average of 2 minutes per year of outage from all causes. The function and interrelationship of the four basic maintenance programs (fault recognition and recovery, diagnosis, trouble location, and error analysis) are detailed here. Results of extensive laboratory testing and early field experience indicate that the maintenance objectives will be achieved despite the size and complexity of the 1A Processor.

The Traffic Service Position System No. 1B (TSPS No. 1B) architecture was conceived to increase performance significantly for future features and traffic growth. The design preserves the TSPS No. 1 software with minimal changes. At the same time, the 3B20 Duplex Processor (3B20D) used in TSPS No. 1B provides additional processor peripherals and a modern programming environment with a real‐time operating system. This paper describes how the TSPS No. 1 software, initially designed to run on the Stored Program Control No. 1A (SPC 1A), executes on the SPC 1B of the TSPS No. 1B. The SPC 1B is a 3B20D tailored for the TSPS application and provides an SPC 1A environment by directly emulating its instruction set. The paper also presents major TSPS application processes and their interaction with the emulated TSPS process and the Duplex Multi‐Environment Real‐Time (DMERT) operating system of the SPC 1B. In addition, the paper describes the integration of TSPS maintenance software into the DMERT maintenance structure.