and provides a current path for external alarm devices.
describes the functions of
the alarm contacts.
Table 5: Alarm Relay Contact Functions
Contact Name
Contact Name
Function
Contact 1
Normally Open (NO)
Current is not flowing through Contact 1 and Contact 2 [REF] when
operating normally. When the current flows, the closed alarm is
generated.
Normally Closed
(NC)
Current is flowing through Contact 1 and Contact 2 [REF] when
operating normally. When the current stops flowing, the open alarm is
generated.
Contact 2
Reference (REF)
Provides the current path for the external alarm-reporting device and
functions as a reference or negative potential terminal for Contact 1.
shows an example of a wiring diagram for a simple output alarm-reporting
device. In this case the device is a light bulb that illuminates when the device encounters a condition
that activates the red alarm LED and relay contacts. The alarm relay contacts can also be used to
activate other devices such as bells or buzzers.
Figure 18: Sample Output Alarm-Reporting Device
58
