Applies To:
  • CitectSCADA 5.xx, 6.xx
  • CitectHMI 5.xx, 6.xx

I am using the scheduled i/o (dialup) feature of CitectSCADA, however occasionally a dialup connection fails. After this, any future attempts to dial out fail with error code -2147483576 (shown in the syslog when dialup debugging is active) and the only way to successfully dial again is to reboot the PC. 

The error code returned by TAPI (Windows' Telephony API) of -2147483576 is in hex 0xFFFFFFFF80000048, which means:

The operation failed for an unspecified or unknown reason.

It was found that the cause of this problem was only present when certain versions of some Microsoft TAPI DLLs existing on a system. Windows XP may suffer from this problem, however Windows 2003 Server should not.

Specifically, it was found that the problem occurred with C:\WINDOWS\system32\tapisrv.dll version 5.1.2600.2716 (xpsp_sp2_gdr.050707-1657).

If you encounter this problem, we recommend you upgrade to Windows 2003 Server, where tapisvr.dll is Version 5.2.3790. 

dial scheduled i/o tapi reboot restart