APC UPS with Compaq Prosignia: Low Battery Signal Fails

• Microsoft LAN Manager, version 2.2

SYMPTOMS

When connecting an American Power Conservation (APC) uninterruptible power supply (UPS) to the serial port of a Compaq ProSignia running Microsoft LAN Manager 2.2 with the low battery signal check enabled in LANMAN.INI, the server shuts down during initialization even under normal UPS operation. Specifically, this happens when the UPS subservice is started, especially on faster 486 machines.

CAUSE

On startup, the LAN Manager UPS service sends a handshake signal to the UPS device by briefly asserting the shutdown signal (the DTR line of the serial port) and the UPS responds by briefly asserting the low battery signal (the DCD line of the serial port). Rather than look for a response to the handshake, the LAN Manager UPS service samples the serial port for the initial state of the UPS. On fast machines it sees the UPS response of the low battery signal, interprets it as a real signal, and begins shutdown.

WORKAROUND

Ignore the low battery settings and set the battery time to an appropriate value (such as 30 minutes = 1800 seconds) in LANMAN.INI:

[ups]
  batterytime = 1800
  signals = 101 

RESOLUTION

The fix for this problem is CSD00.060.

Additional query words: 2.20 2.2

Keywords :
Version : :2.2
Platform :
Issue type :