CSL DUALCOM PRO 4 Manual page 20

The DualCom Pro Fire uses a normally closed configuration so that a power fail on
the Fire Alarm Panel will signal an alarm to the Gemini Global Platform.
If the circuit is broken, then an open circuit tamper alarm will be generated
If it detects 0v, then a short circuit tamper alarm will be generated
If the wrong resistor values have been used, then a fault tamper alarm will be
generated
Resistors
These are the colour code markings for the 10k Ohm and 4k7 Ohm resistors
respectively.
Self-Learn
If the self-learn functionality (Press Button C for 5 seconds) is invoked when an EOL
pin is Alarm State then the DualCom Pro Fire will switch to generating a Restore
event when a high voltage is detected for that pin going forward and an Alarm event
when a low voltage is detected.
Relays
The relays are intended to notify the Fire Alarm Panel of events on the DualCom Pro,
Gemini Global Platform or from the ARC. Their configuration is fixed in Fire Mode and
cannot be changed via My Base.
When the DualCom Pro is unpowered, NC is connected to C and NO is not connected