Signals Used by the UPS Service

Windows NT uses a serial (COM) port to connect to the UPS. Table 20.1 shows the signals that the Windows NT UPS service uses to communicate with the UPS, the associated pin numbers, and the function each signal provides to the UPS service. You need to know which of these signals your UPS supports so that you can configure the UPS service.

If you use a UPS service provided by your UPS vendor, the signals and their usage will probably be different than the signals that the Windows NT UPS service uses.

Table 20.1 UPS serial port connections

RS-232 Signal

9 Pin Connector Pin #

25 Pin Connector Pin #

UPS Usage

CTS

8

5

Power failure

DCD

1

8

Low battery

DTR

4

20

UPS shutdown


In the UPS Configuration group box, check the boxes that correspond to the signals that your UPS supports. For each of these signals, the UPS Interface Voltages (negative or positive) indicates the voltage present when that event occurs.

Low Battery Signal

When the UPS battery begins to run low, the UPS uses this signal to notify the UPS service.

When fully charged, UPSs typically deliver from five to 20 minutes of DC power after AC power has failed. If your UPS can detect when the battery is running down, you should check the low battery signal box in the UPS Configuration group box.

If you do not check the low battery signal box, the UPS service uses the information in the UPS Characteristics group box to estimate how much time remains on the battery after a power failure.

Remote UPS Shutdown

You want to conserve the life of the UPS battery for as long as possible. The UPS service uses the UPS Shutdown signal to notify the UPS that Windows NT has completed its orderly shutdown and that the UPS can shut off power to the computer.

Power Failure Signal

The power failure signal is generated by the UPS to signal the UPS service that a power failure has occurred. The Windows NT processing that occurs when it receives this signal depends upon whether the UPS can send a low battery signal.

If the UPS can send a low battery signal:

If the UPS cannot send a low battery signal: