The APC Smart-UPS series models 900, 900XL, 1250, and 2000 systems
include a standard RS-232 line failure output and UPS shutdown input.
The low battery signal, however, is not a standard RS-232 signal and
requires special configuration for use with Windows NT.
For RS-232 outputs and inputs, the line failure, low battery, and UPS
shutdown signals can be connected from the UPS to one of the computers
RS-232 (serial) ports. Because the low battery signal generated by the
APC Smart-UPS is an open collector output, it must be pulled up to a
common reference voltage by means of a pullup resistor.
Following is the configuration for a cable that can be used with the
APC Smart-UPS series, including the implementation of the pullup
resistor.
DB9 9 Pin Female Connector DB9 9 Pin Male Connector
(to PC serial port) (to UPS connector)
Pin #5------ Ground ----------Pin #4
Pin #8------ Power Failure--- Pin #2
Pin #4------ UPS Shutdown---- Pin #1
Pin #1------ Low Battery----- Pin #5 --[10k ohm]-- Pin #8
The above diagram indicates that Pin #5 on the PC serial port should
be connected directly to pin 4 on the UPS side, pin 8 to pin 2, pin 4
to pin 1, and pin 1 to pin 5. In addition, pins 5 and 8 on the same
side (the UPS side) have a 10k ohm (10,000 ohm) resistor connected
between them. This resistor serves to pull the voltage on this
non-RS-232 output high until an actual low voltage is generated by a
low battery condition.
With the above cable, the following polarities should be set in the
UPS section of the Control Panel:
Power failure signal: Positive
Low battery signal: Negative
Remote UPS shutdown: Positive