LT Modem AT Commands:

I3  - displays driver revision
I9  - displays Country setting (Changed by Windows' Dialing Properties)
I11 - displays current (or last) call rate & diagnostic info
    (Note - With Windows98 and some driver versions, you will not be able to view data in I11 after a DUNs session; you'll have to use a terminal program (HyperTerminal) to place a call to see valid diagnostic data.

-V90=# where # can be any of the following to control the V90 downstream rate:
0  V.90 disabled
1 Auto Rate (default)
2 28000          3 29333            4 30666
5 32000          6 33333            7 34666
8 36000          9 37333           10 38666
11 40000         12 41333           13 42666
14 44000         15 45333           16 46666
17 48000         18 49333           19 50666
20 52000         21 53333           *22 54666  
23 56000*   
* 22 & 23 valid only with 5.49(+) driver

S38=#  where # disables or selects the KFlex downstream rate:

0 - disable KFlex (will force V90 -or- v.34 connection)
1 - Auto Rate (default)
2 - 32k            3 - 34k            4 - 36k
5 - 38k            6 - 40k            7 - 42k
8 - 44k            9 - 46k           10 - 48k
11- 50k           12 - 52k           13 - 54k

s37=#  where # controls the upstream rate:

0 - Maximum (default)
3 - 300bps         5 - 1200bps        6 - 2400bps
7 - 4800bps        8 - 7200bps        9 - 9600bps
11- 14.4k         13 - 19.2k         14 - 21.6k
15- 24k           16 - 26.4k         17 - 28.8k
18- 31.2k         19 - 33.6k
 

Default \N3 allows V.42, MNP, or buffered (NoEC) mode.   To use V.42 only, the command is \N4.  Default %C1 will use V.42bis compression when V.42 error control is used.

COUNTRY SELECT:
To configure for a specific country, execute the following AT command:

%T19,0,country_code in HEX

Country_Code in HEX:

Note - The country code determines homologation parameters - settings that determine dial-tone, ring, busy detection, etc. These parameters can be further modified with AT%21,x,y commands which are documented at page 64 of the command reference (see .pdf link below).

Other AT Commands:

The Agere site had .pdf-format 87-page Reference Manual (Host-Based Controler Modem AT Command Set). This document, also available from Modemsite downloads, includes V.90/V.42, but not V.92/V.44-related commands. Modemsite's V.92 Commands page includes information on the V.92/V.44 commands.