DPS Telecom D-PK-NGDLT, User Manual

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13
Contact to Ground
– Batt.
Alarm
Dry Contact
– Batt.
GND
Alarm
NetGuardian LT G2 case
NetGuardian LT G2 case
Note: Make sure that grounds have a common reference —
this is usually done by tying grounds together.
GND
Form -C Contact
NetGuardian LT G2 case
C
NC
NO
X
_
Fig. 5.3.2 Discrete alarm points can connect as a dry contact, a contact to ground, or a Form-C contact
The discrete alarm inputs are also called digital inputs or contact closures. Discrete alarms are either activated or
inactive, so they're typically used to monitor on/off conditions like power outages, equipment failures, door alarms
and so on.
The unit's discrete alarm points are single-lead signals referenced to ground. The ground side of each alarm point
is internally wired to ground, so alarm points can connect either as a dry contact or a contact to ground.
In a dry contact alarm, the alarm lead brings a contact to the ground lead, activating the alarm. In a contact to
ground alarm, a single wire brings a contact to an external ground, activating the alarm.