Single Digital Input ModulesOn Sing

Single Digital Input ModulesOn Single Digital Input Modules, only those portions of the signal path which are required to ensure safe operation are triplicated. Single modules are optimized for those safety-critical applications where low cost is more important than maximum availability. Special self-test circuitry detects all stuck-On and stuck-Off fault conditions within the non-triplicated signal conditioners in less than half a second. This is a mandatory feature of a fail-safe system, which must detect all faults in a timely manner, and upon detection of an input fault, force the measured input value to the safe state. Because the Tricon controller is optimized for deenergize-to-trip applications, detection of a fault in the input circuitry forces to Off (the deenergized state) the value reported to the Main Processors by each channel.Digital Output ModulesEvery Digital Output Module houses the circuitry for three identical, isolated channels. Each channel includes an I/O microprocessor which receives its output table from the I/O Processor on its corresponding Main Processor. All of the Digital Output Modules, except the dual DC modules, use a patented quadruplicated output circuitry, referred to as Quad Voter, which votes on the individual output signals just before they are applied to the load. This voter circuitry is based on parallel-series paths which pass power if the drivers for Channels A and B, or Channels B and C, or Channels A and C command them to close—in other words, 2-out-of-3 drivers voted On. Dual Digital Output Modules provide a single series path, with the 2-out-of-3 voting process applied individually to each switch. The quadruplicated output circuitry provides multiple redundancy for all critical signal paths, guaranteeing safety and maximum availability.