56k Modem Troubleshooting - Init Strings & Extra Settings

Disabling 56k - Protocol/Modulation Select

Click here to see how to get to the screen where you enter these modem initialization strings.

Extra settings to control modulation: (also see Limiting Your Connect Speed)

Modem	Disable x2	Disable v.42	Disable V.90	Disable V.90 & x2	Disable V.92
Sportster/USR	S32=34	S15=128	S32=66	S32=98	s32=128 +PCW=2 +PIG=1 +PQC=3
Courier	S58=1	S27=32	S58=32	S58=33
Cirrus MD56xx	+MS=V90,0	+ES=4, 4, 6 %C1	+MS=X2,0	+MS=V34,1,0,33600
ESS / Teledrive	+MS=17,0	\N5	+MS=12,0	+MS=11,0
Broadcom BCM	S51=95	\N5	S51=63	S51=31
	Disable KFlex	Disable V90	Disable V90&Flex	Disable v.42	Disable V.92
Rockwell ACF V2.x	+MS=12	+MS=56	+MS=11	&Q6
Rockwell HCF & Soft56 & ACF V3.x	+MS=V90,0	+MS=K56,0	+MS=V34	+ES=1,0,1;
Lucent Soft & all Agere V.92 modems	n/a (K56Flex not supported)	+MS=V34	+MS=V34		+MS=V90
Lucent LT	s38=0	-v90=0	s38=0-v90=0	\n2	+MS=V90
Lucent Venus	s109=2	s109=0	s38=0	\n2	+MS=V90
PCTel HSP	n0s37=14	n0s37=13	n0s37=12	\N5
Motorola SM56	MM15 -or- +MS=V90,0*	MM13 -or- +MS=K56FLEX,0*	MM12 -or- +MS=V34*
VIA	MM15 -or- +MS=V90,0*	MM13 -or- +MS=K56FLEX,0*	MM12 -or- +MS=V34*	+ES=4,0,1
ST Micro / SGS	+MS=90	+MS=56	+MS=34
Smartlink	+MS=90	+MS=56	+MS=34	\N5
TOPIC	(only V.90 available)	&U1	&U1	\N3

V.92 Modems: I do not have complete information on how all the various V.92 modem chipsets behave; however, "disabling" V.92 is usually achieved by selecting V.90 or lower protocol. Each of the V.92 enhancements - quick connect, modem-on-hold, and PCM upstream - can be enabled or disabled by V.92 Commands. Information on strings to disable V.44 compression is also on V.92 Commands.

Rockwell-based modems: If you are getting the PORT speed instead of modem speed, put W2 in extra settings. Rockwell 56k modems also have an extended-format +MS= command; see Limiting Your Connect Speed. *- Rockwell/Conexant ACF chipset with firmware versions beginning with 3.x use the HCF & Soft56 command format. Versions beginning with 2.x use the 'Rockwell Dual' command set.

+MS= options
Many modems that support +MS= command have additional options not listed to force the modem to even lower speeds / connection protocols including:
   +MS=V21    - 1200 baud
   +MS=V22    - 2400 baud
   +MS=V32    - 9600 baud
   +MS=V32B - 14.4k bps

More info on +ES= error control options: Modems that support +ES commands will usually conform to the following:

Command Options
+ES=     p,q,r
p options: Specifies the originate-modem’s Request Error Correction
0 Direct mode
1 Normal mode
2 LAP-M Only
3 LAP-M or MNP
4 MNP Only
6 Initiate Sync Access modem when connection is established
q options: Specifies the answer-modem’s Fallback Error Correction
0 EC optional, fallback to Normal mode
1 EC optional, fallback to Direct mode
2 EC required (LAP-M or MNP)
3 EC required (LAP-M only)
4 EC required (MNP only)
r options: Specifies the originate-modem’s Fallback Error Correction mode
0 Direct mode
1 Normal mode
2 EC optional, fallback to Normal mode
3 EC optional. Fallback to Direct mode
4 EC required (LAP-M or MNP)
5 EC required (LAP-M only)
6 EC required (MNP only)
8 Initiate synchronous access mode when connected

Lucent-based modems: More info on some of the other options for the LT Win Modem is here, and in Limiting Your Connect Speed.

Texas Instruments-based modems: If you have a Texas Instruments chipset and it's not a 3Com/USR modem, the modem may be made under license from 3Com using 3Com-supplied firmware that you must get from the licensee. These modems will support the same commands and operate similarly to 3Com/USR modems. Others (CirrusLogic & ?) may have independently-developed firmware using their own command set.
COUNTRY INFORMATION:
Some modems implement a +GCI command to set country of installation:
+GCI=## = Set country in which modem is installed
00 Japan
04 Germany
09 Australia
0A Austria
0F Belgium
16 Brazil
20 Canada
2E Czech Republic
31 Denmark
3C Finland
3D France
42 Germany
50 Hong Kong
57 Ireland
58 Israel
59 Italy
6C Malaysia
7B Netherlands
82 Norway
8B Portugal
8C Singapore
9F South Africa
A0 Spain
A5 Sweden
A6 Switzerland
A9 Thailand
AE Turkey
B4 United Kingdom
B5 USA
If you have a properly installed modem .inf file, you normally don't need any initialization string or extra settings when using DUNS (dial-up-networking) - the .inf file determines the init string which - when everything works right - gives you the best connection possible. But, it doesn't always work that way, and sometimes you can improve your connection by adding extra settings (additional initialization string). Many command formats are specific to different modem chipsets. Below the screenshot showing where you go to add extra settings are some 56k/V.34-related commands for various modem chipsets. These commands can be used to enable or disable 56k (V.90, x2, K56Flex, or no-56k- V.34), error correction and compression protocols (V.42/MNP).