GAI-Tronics 379-002 Monitored RElay Module (MRM) Stations - Manual (Page 8)

Pub. 42004-491A
Model 379-002 Monitored Relay Module Station Page 8 of 13
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Mode 3: IDC Single Normally-Closed (N.C.) Switch
In this configuration, only one normally-closed dry contact closure may be installed per supervised line.
In this mode, the loop is monitored for open circuits, wire-to-wire short circuits (across + and –), and
ground faults. When the contact closure is not active (closed), the 15 k
 is bypassed and the circuit sees
only the 5.1 k  load.
Figure 6. IDC Single Normally-Closed Switch
This change is sensed by the MRM and indicates to the MRM that the contact closure is active. If there is
a short across L1 and L2, if either leg is grounded, or if a break occurs on either leg, the MRM indicates
that a fault has occurred.
N OTE : The terminating resistors are not included with the MRM. These resistors are included in a kit
(12509-004), which must be ordered separately.