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6.0 COMMUNICATION
6.1 DB-9 Connector
The UPS has a DB-9 (9 pin female) connector on the rear to allow UPS status communications with a
computer running Liebert MultiLink shutdown software. The connection provides serial communica-
tion, On Battery and Low Battery signals. Liebert MultiLink software and a 6 ft. (1.8m) DB-9 serial
cable are shipped with the UPS.
When power is interrupted and battery power is low, Liebert MultiLink software can signal the host
computer to gracefully shut down the operating system.
6.2 Remote Shutdown Via the DB-9 Connector
The Liebert PSI XR can be shut down remotely by shorting Pins 5 and 6 or via Pins 4 and 5 of the DB-
9 connector.
6.2.1 Any Mode Shutdown Via Pins 5 & 6
When Pin 6 is shorted to Pin 5, the UPS output is shut Off no matter what mode the UPS is operat-
ing. The UPS cannot be started as long as the pins are shorted. When the short is removed, the UPS
output can be enabled by pressing the ON/Alarm Silence/Manual Self-Diagnostic button.
6.2.2 Battery Mode Shutdown Via Pins 4 & 5
While the UPS is operating on battery, a 5-12VDC signal for 2 seconds or longer is required to signal
a shutdown. Signals for less than 2 seconds are ignored.
After Pin 4 receives the shutdown signal, a 2-minute shutdown timer begins a countdown. The shut-
down timer cannot be stopped: If utility power returns during the 2-minute countdown, the shutdown
timer continues until the end of 2 minutes and the UPS turns Off. The UPS will restart 10 seconds
after utility power returns.
Table 4 DB-9 pin assignment
DB-9 Pin Assignment Description
1 Low Battery (open collector)
2 UPS TxD
3 UPS RxD
4 Remote Shutdown (5-12V); on-battery operation
5 Common
6 Output Off, (short to Pin 5, non-latching); any mode operation
7 Low Battery (open emitter)
8 Utility Fail (open emitter)
9 Utility Fail (open collector)
Pin Assignment Collector to Emitter*
54321
6789
(-)
(+)
330 Ohms
Open
Collecto
r
Open
Emitter