Evolution of Fault Tolerant Switching Systems in AT&T

  • George F. Clement
  • Paul K. Giloth
Part of the Dependable Computing and Fault-Tolerant Systems book series (DEPENDABLECOMP, volume 1)


Fault tolerant hardware and software architectures for analog/digital electronic telephone switching systems have evolved over the last 30 years at AT&T Bell Laboratories and have been deployed extensively in several generations of telephone switching and support systems. Fault tolerance has been necessary as large complex systems are never fault free. The techniques employed detect errors, correct errors, reconfigure the system, reinitialize the system automatically, and in general provide for system integrity under all operating and fault situations. The ultimate quality of performance depends on how well the fault tolerant techniques have been implemented. The fault tolerant techniques developed for communication systems are also useful in many other applications where real-time, continuous system operation is mandatory. A summary of these hardware and software fault tolerant techniques are provided with application data to demonstrate effectiveness. As part of the maintenance strategy, “expert systems” were developed and deployed and have continued to evolve. They provide excellent automatic maintenance support for several thousand switching systems.


Switching System Hardware Failure Fault Recovery Software Integrity Hard Fault 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag/Wien 1987

Authors and Affiliations

  • George F. Clement
    • 1
  • Paul K. Giloth
    • 1
  1. 1.AT&T Bell LaboratoriesNapervilleUSA

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