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Follow this instruction for enable V90 / X2 protocol
in your USRobotics Courier modem.
(only for 20.16Mhz modems)

Version 1.2.5 :)

Step 1. Download next the following files:
freelsd.zip - universal firmware uploader into USR Courier modem and sdl extractor.
250297x2.exe - original USR firmware (x2) for 20.16 Mhz

Step 2. Unpack all these files and do the following commands:
loadsdl.exe sdl20.exe 1 2
int2bin.exe 1 x2.bin
Step 3. Apply this patch for file 'x2.bin':
00000A1F: 42 22
00000A22: 48 28
0000D8AB: 74 EB
0000D8F0: 73 EB
0000D8F1: 07 09
00014718: 8F FF
0001F42E: 00 01
0001F42F: 00 06
000240B6: 74 EB
00024F11: 75 EB
00024F12: D1 0C
example: seek to offset 0D8F1h in file, ensure the byte is 07h, and change it to 09h value.
note: also you may use already patched x2.bin file (x2.hck).

 Step 4. Execute freelsd.exe with already patched file:
freelsd.exe /c1 /r x2.bin
warning: /c1 - COM1, you must use your port settings.
note: run freelsd.exe under DOS, under WIN/NT they dont work.

Step 5. Start any terminal program, and send the following string into your modem:
at&f1&w
atc23=7c39=31c56=0c74=0
atc8=31
atnx

 Step 6. Wow! Now, you have a modem with X2 protocol in active and V90 in passive. ;)

Step 7. If u needed V90 protocol, burn V90 firmware from official 3Com/U.S.Robotics site.

Bonus.
  • s39 - outlevel (for US/Canada).
  • busy fix.
  • firmware adapted for other then US/Canada country models.
  • you can change counry code on the fly: atc10=??nx
    where ?? is value from the following Country Code list
    0 - US/Canada
    1 - Japan
    2 - Finland
    3 - Sweden
    4 - UK
    5 - Norway
    6 - Switzerland
    7 - Netherlands
    8 - South Africa
    9 - Italy
    10 - New Zealand
    11 - Czechoslovakia
    12 - Belgium
    13 - Denmark
    14 - Australia
    15 - France
    16 - Germany
    17 - International
    18 - Austria
    19 - Ireland

    Signed,
    FreeLSD.