Importance

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Abstract

An improved field instrumentation system employing optical multiplex transmission in which data from a plurality of field devices, including both sensors and controllers, are transmitted through an optical distributor, such as a star coupler, to a master processor at a control panel location as well as to other field devices. The optical distributor branches and couples in a ratio of N:N, the data which are transmitted bidirectionally through the various optical transmission paths connected to the field devices to form the basis of a control loop located in the field. A submaster processor, located in the field and coupled to the optical distributor, is automatically substituted for the master processor in the event that the master processor is disabled. The overall reliability of this system is thereby markedly improved.

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First Claim