Brickcom NR-1604 \ User Manual page 68

3.5.6 UPS Configuration
The UPS allows the NR-1604 to receive an uninterrupted power supply in
the event of a power failure. Through the UPS, the NR-1604 is able to
detect if there is a power failure and automatically shut itself down after a
period of time, ensuring that the user does not experience an abrupt
interruption in their video recording.
To send and receive signals between the UPS and the NR-1604, connect
the UPS to the NR-1604 using the DI/DO port. Refer to the diagram below
to connect the UPS's RS-232 interface to the NR-1604 DI/DO port.
Note: the NR-1604 will use D1-1 to receive signal from the UPS
system and DO-2 to shut down.