A “Strongly-Fail-Safe Majority Voted Output” Circuit used for Designing Dependable Computer Systems

  • Serge Noraz
  • Michel Prunier
Part of the Dependable Computing and Fault-Tolerant Systems book series (DEPENDABLECOMP, volume 8)


As part of critical application used in railways transportation, space, chemical and nuclear industries, the processing part which controls the actuators of the electromechanical part is realized with fail-safe circuits. But these give us to the following problems:
  • Complexity of design in case of redundant solutions, done till now, which require conventional fail-safe circuits.

  • Necessity of off-line test sequences in case of non-redundant solutions involving “strongly-fail-safe” circuits.

This paper aims to provide a practical solution using “strongly-fail-safe” circuit for designing dependable computer systems aimed at critical processes. The goal is to make use of such systems easier, to avoid the drawbacks generated by off-line test phase and to obtain the best “cost-safety” compromise. First of all, we introduce the scheme of a “strongly-fail-safe” basic cell without any off-line test equipments. The advantage is to obtain a “strongly-fail-safe” circuit which requires few components. Then, we suggest an architecture of a “strongly-fail-safe majority voted output” circuit designed from the “strongly-fail-safe” basic cell. The reliability, the availability and the safety of this “majority voted output” mechanism is assessed. For information a triple modular redundancy computer system including this last mechanism is compared with well-known dependable computer systems. The good results obtained show that such a solution may meet a wide range of safe applications because of its low complexity and its fitness to be easily implemented. In conclusion a quantitative and a comparative study is performed. It involves two dependable redundant computer architectures suggested for an industrial refinery project need.


CMOS Inverter Triple Modular Redundancy Full Duplex Combine Fault Functional Input 
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 1993

Authors and Affiliations

  • Serge Noraz
    • 1
  • Michel Prunier
    • 1
  1. 1.Safety and Electronic Systems (SES) DepartmentMerlin GerinGrenoble CedexFrance

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