Each F80x module monitors the output of the eight fieldbus

segments and indicates an alarm by means of a built-in, normally closed

relay if any of the segments is shorted, or below the minimum output

voltage threshold. Failure of either of the bulk power input supplies

is also annunciated. The alarm contacts are volt-free and galvanically

isolated from other circuitry. Connections to the alarm relays are made

via terminals on the F890-CA carrier. A separate alarm module is not

required for this function. LED indicators also show the status of each

F80x module and the eight individual segments. In normal operation,

each segment LED is lit, showing that the segment is powered. If a

segment is shorted, this LED is extinguished, and the module Alarm

LED is lit.