Microsoft KB Archive/250649

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Description of the Modem Settings Key in the Windows Registry

Article ID: 250649

Article Last Modified on 1/27/2007


  • Microsoft Windows Millennium Edition
  • Microsoft Windows 98 Second Edition
  • Microsoft Windows 98 Standard Edition
  • Microsoft Windows 95

This article was previously published under Q250649

If this article does not describe your hardware-related issue, please see the following Microsoft Web site to view more articles about hardware:

IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry


This article describes the Modem Settings registry key in the Windows Me/98/95 Registry. This key is located in



WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
The Settings key contains commands for configuring various modem settings. After the Init key commands are sent, Windows builds a dynamic configuration command string by concatenating various entries shown in the following table. The command depends on the settings selected in the modem's properties.

The following table describes the entries under the Settings registry key:

Subkey Description Example
Prefix Configuration command prefix AT
Terminator Configuration command suffix <cr>
DialPrefix Dial command prefix D
Dial_Pulse Use pulse dialing P
Dial_Tone Use tone dialing T
Blind_Off Detect dial tone before dialing X4
Blind_On Do not detect dial tone before dialing X3
CallSetupFailTimeout Specify call setup time-out S7=<#>
InactivityTimeout Specify inactivity time-out S30=<#>
SpeakerVolume_Low Low speaker volume L1
SpeakerVolume_Med Medium speaker volume L2
SpeakerVolume_High High speaker volume L3
SpeakerMode_Off Speaker always off M0
SpeakerMode_Dial Speaker on during dial and negotiation M1
SpeakerMode_On Speaker always on M2
SpeakerMode_Setup Speaker on only during negotiation M3
FlowControl_Off No flow control &K0
FlowControl_Hard Hardware flow control &K1
FlowControl_Soft Software flow control &K2
ErrorControl_Off Error control disabled (normal mode, not direct) +Q6S36=3S48=128
ErrorControl_On Error control enabled (auto reliable) +Q5S36=7S48=7
ErrorControl_Forced Error control required to connect (reliable) +Q5S36=4S48=7
ErrorControl_Cellular Cellular protocol enabled \N3-K1)M1-Q1*H1
Compression_On Compression enabled S46=138
Compression_Off Compression disabled S46=136
Modulation_CCITT Use CCITT modulations for 300 and 1200 bps B0
Modulation_Bell Use Bell modulations for 300 and 1200 bps B1
SpeedNegotiation_Off Connect only at default modem speed; do not fall back N0
SpeedNegotiation_On Use lower DCE speed to connect, if necessary N1

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