WinNT Appears Not to Send DTR Signal to a UPS on Shutdown

• Microsoft Windows NT Workstation versions 3.51 and 4.0
• Microsoft Windows NT Server versions 3.51 and 4.0

SYMPTOMS

When Windows NT goes through the shutdown process after a low battery message, it appears that Windows NT does not send a DTR signal and the UPS does not power off.

CAUSE

Windows NT waits approximately 2 minutes before sending out the DTR signal, allowing enough time for programs and services to shutdown properly. It is possible that the UPS will run out of power and perform a manual shutdown before Windows NT sends the DTR signal.

RESOLUTION

It is possible to change the amount of time that elapses from when the Low Battery message is sent and when Windows NT sends out the DTR signal. You can use Registry Editor (Regedt32.exe) to add an entry to the registry.

NOTE: You must be logged on with administrative permissions to alter certain registry settings.

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it.

To specify a shut down wait, perform the following steps:

1. Start Registry Editor (Regedt32.exe) and go to the following subkey:

         HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\UPS
   

2. From the Edit menu, click Add Value. Type the value ShutdownWait with a REG_DWORD value in seconds between zero and 600 decimal.

3. Quit Registry Editor and restart your computer for the changes to take place.

MORE INFORMATION

For more information, please see the following article in the Microsoft Knowledge Base:

   ARTILCE-ID: Q98885
   TITLE     : Pin Connections for Cabling Between APC UPS and RS-232