DPS Telecom NetGuardian LT G2 User Manual page 19

Dry Contact
NetGuardian LT G2 case
– Batt.
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.
GND
Alarm
Form -C Contact
NetGuardian LT G2 case
_
X
Contact to Ground
NetGuardian LT G2 case
GND
Alarm
– Batt.
Note: Make sure that grounds have a common reference —
this is usually done by tying grounds together.
NC
C
NO
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