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Q258838: Dial-Up Networking Automatic Redial May Stop After 15 Attempts

Article: Q258838
Product(s): Windows for Workgroups and Windows NT Networking Issues
Version(s): WINDOWS:95; winnt:4.0
Operating System(s): 
Keyword(s): kb3rdparty kbhw dun kbHardware kbDialUp
Last Modified: 08-AUG-2001

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The information in this article applies to:

- Microsoft Windows 95 
- Microsoft Windows 98 
- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Workstation version 4.0 
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SYMPTOMS
========

If you have a dial-up connection configured to automatically redial your
Internet service provider (ISP), you may receive the following error message
after the fifteenth automatic redial attempt:

  Could not detect modem. It may be in use, turned off, or not installed
  properly

CAUSE
=====

Newer modems that are based on the Rockwell chip set, and U.S. Robotics/3Com
modems may have "blacklisting" enabled (this may be country-specific, depending
on the manufacturer of the modem). After 15 attempts the modem, in accordance
with ITU standards, "blacklists" the phone number. When this occurs, you cannot
redial the number until an internal modem time-out has expired or you reboot the
computer.

RESOLUTION
==========

Modify the modem initialization string to include one of the following commands.
Please refer to the documentation for your modem for details.

+------------------------------+
| Command | Modem type         | 
+------------------------------+
| %TCB    | Rockwell based     | 
+------------------------------+
| S40=2   | U.S. Robotics/3Com | 
+------------------------------+
| S40=7   | U.S. Robotics/3Com | 
+------------------------------+

This command prevents the modem from "blacklisting" a number and allow repeated
redials up to 99 times.

STATUS
======

This behavior is a limitation of the modem configuration files supplied with
your modem. Contact your modem manufacturer for updated files. To support
delayed and "blacklisted" responses, the modem's unique ID .inf file should
contain the necessary registry keys.

MORE INFORMATION
================

Most modern modems keep a table of the most recently dialed numbers in memory
with a count against each number dialed. Commonly, after a number has been
dialed 15 times, the modem refuses to dial the number again until a certain time
period has elapsed, thus "blacklisting" or delaying the number.


Additional query words: delayed

======================================================================
Keywords          : kb3rdparty kbhw dun kbHardware kbDialUp 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbWin95search kbWin98search kbZNotKeyword3 kbWin98
Version           : WINDOWS:95; winnt:4.0
Issue type        : kbprb

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