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COMMUNICATIONS
Communications Interface Port
The Liebert GXT2U UPS has a standard DB-9 serial port female connector
located on the rear of the UPS unit. Several signals are provided on this port
and are assigned as follows:
* Maximum voltage and current on pins 1, 7, 8, and 9 is 60VDC; 10.0 mA.
Pins 4 & 5 - Remote Shutdown on Battery
1. This pin is functional only when the UPS is in battery mode. If the UPS is
being powered by the utility, Pin 4 will ignore any signal on this pin.
2. Pin 4 requires a 5-12 VDC signal to shutdown. This normally comes form
the serial port using Liebert’s contact closure cable. It cannot be used with
just a contact closure unless the relay is used to switch a voltage source. A
5-12 VDC signal for 1.5 seconds or greater is required to signal a shutdown.
Signals for less than 1.5 seconds will be ignored. After Pin 4 receives a shut-
down signal for 1.5 seconds, the command cannot be canceled.
3. A battery shutdown signal on Pin 4 will NOT cause an immediate shut-
down. A shutdown signal will start a 2-minute shutdown timer. The timer
cannot be stopped. After 2 minutes, the UPS will shut down.
4. If the utility returns during the 2-minute timer countdown, the shutdown
timer will continue until the end of 2 minutes and the UPS will turn OFF.
The UPS must remain OFF for at least 10 seconds even if AC input power
returns before the UPS turns OFF. This serves to reset and restart the
server.
Whether the UPS turns back ON when power is restored depends on the auto-
restart setting: enabled or disabled.
If the auto-restart is disabled, the UPS will not restart after performing the
2-minute shutdown delay.
Pin Assignment Description
1 Low Battery (open collector)
2 UPS TxD (typical RS-232 levels)
3 UPS RxD (typical RS-232 levels)
4 Remote Shutdown (5-12VDC, 10-24 mA max); battery operation
5 Common
6 Remote Shutdown (short to pin 5); all modes of 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
DISCONTINUED
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