Honeywell Silent Knight IFP-2000 Module 3 Installation Manual page 62

Intended for fire door applications
When there are no alarms in the system and the
panel has AC power, door holder circuits have
24-volt power present at their terminals
Any alarm will cause power to disconnect
Power will be re-applied when the system is reset
If AC power is off for more than 15 seconds
Door holder power will be disconnected to conserve the
battery backup
When AC power is restored, power is immediately restored to
circuits
Door Holder Door Holder