1A Processor: Maintenance Software

Like the processors for the earlier electronic switching systems (e.g., No. 1 ESS, No. 2 ESS), the 1A Processor depends on integrating maintenance software with the hardware to (t) quickly recognize a fault condition, (ii) isolate and configure around the faulty subsystem, (iii) diagnose the faulty unit without interfering with normal processor functions, and (iv) assist the maintenance personnel in locating and correcting the fault. The system usually detects a fault and reconfigures itself within a few milliseconds without affecting calls being switched through the office. The 1A Processor writable program stores and high-throughput disk and tape subsystems, including direct memory access, have introduced both new maintenance problems and new avenues for their solution. Although these bulk storage systems have complicated the process of fault recognition and diagnosis, they have also provided the key to vastly improved trouble location and error analyEach aspect of maintenance software is designed to minimize the likelihood of system outages. As discussed in Ref. 1, a reliability objective 255