DigitalFlow™ GF868 Startup Guide (1 and 2-Channel) 13
Chapter 1. Installation
1.7.5 Wiring an Alarms Option Card
The GF868 can accommodate 1 to 6 alarm option card(s). Each alarm option card provides three Form C relays
(A, B and C). The alarm relays on the option card are available in two types:
• general-purpose
• hermetically-sealed for Class I, Division 2 hazardous areas.
Chapter 4, Specifications, lists the maximum electrical ratings for the relays. Each alarm relay can be wired as
Normally Open (NO) or Normally Closed (NC).
In setting up an alarm relay, it may be wired for either conventional or fail-safe operation. In fail-safe mode, the alarm
relay is constantly energized, except when it is triggered or a power failure or other interruption occurs. See Figure 6
for the operation of a NO alarm relay in both conventional and fail-safe mode.
Connect the two alarm wires required for each relay in accordance with the pin number assignments shown in Figure 9
on page 18.
Figure 6: Conventional and Fail-Safe Operation
C
NO
NC
NC
C
NO
NC NC
C
NO
C
NO
Monitoring
Alarm
Device
Monitoring
Alarm
Device
Monitoring
Alarm
Device
Monitoring
Alarm
Device
not triggered
Conventional,
not triggered
Fail-Safe,
triggered
Conventional,
triggered or power failure
Fail-Safe,
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