925-0290 Rev A 7
4.0 FAIL-SAFE SELECTION
4.1 Description
A Fail-Safe condition means that the relay contact positions are set up so that in the event of a power fail-
ure the relay will be de-energized and the contacts will indicate a condition that is deemed safe for the
application. (Refer to FIGURE 2.1 for the location of the Fail-Safe selection switch.)
4.2 Fail-Safe High
Fail-Safe High means that the relay will be energized when the probe is uncovered and will de-energize
when the probe is covered. In this mode, a power failure will cause the relay contacts to indicate that the
probe is covered whether it is or not.
4.3 Fail-Safe Low
Fail-Safe Low means that the relay will be de-energized when the probe is uncovered and will energize
when the probe is covered. In this mode, a power failure will cause the relay contacts to indicate that the
probe is uncovered whether it is or not.
NC C NO NO C NC
1 1 1 2 2 2
NC C NO NO C NC
1 1 1 2 2 2
UNCOVERED COVERED
FAIL SAFE "HIGH" RELAY CONTACT POSITION
NC C NO NO C NC
1 1 1 2 2 2
NC C NO NO C NC
1 1 1 2 2 2
UNCOVERED COVERED
FAIL SAFE "LOW" RELAY CONTACT POSITION
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