U.S. Robotics Sportster 28800 Modem Does Not Function with RAS

The information in this article applies to:

• Microsoft Windows NT Workstation versions 3.5 and 3.51
• Microsoft Windows NT Server versions 3.5 and 3.51

SYMPTOM

Some models of the U.S. Robotics Sportster 28800 V.34 and V.FC modems do not work with Remote Access Service and some other communications software. However, the same modems sometimes appear to function properly with Windows Terminal or other communications software.

CAUSE

The U.S. Robotics Sportster 28800 V.34 modem is not on the Windows NT 3.51 Hardware Compatibility List (HCL). Some newer U.S. Robotics Sportster 28800 V.34 and V.FC modems have updated circuitry or firmware. The updated modems function like a U.S. Robotics Sportster 33600/Fax V1.0 or V1.1 modem instead of a Sportster 28800. When you use a similar model to connect to the Sportster 28800, the two modems appear to connect at 33,600 baud. There are some differences with the initialization strings of the Sportster 28800 and the 33600 model.

To verify the firmware version of your U.S. Robotics Sportster fax/modem:

1. Start the Terminal tool in the Windows NT Accessories group.

2. Properly configure the communications settings for your fax/modem.

3. Type "ATI3" (without quotation marks). This will tell you which firmware version you have.

RESOLUTION

To correct this problem, do one of the following:

• Obtain an updated Modem.inf file from U.S. Robotics at (847) 982-5151 (technical support) or (847) 982-5092 (BBS).

  -or-

1. In Terminal type the following:

          ATI3
   

       - If the modem responds with "Sportster 33600/Fax V1.0," proceed with
         step 2.
   

       - If the modem responds with "Sportster 33600/Fax V1.1," proceed with
         step 2, except that you will have to change the following:
   

            DETECT_RESPONSE=Sportster 33600/Fax V1.0
   
         to this:
   
            DETECT_RESPONSE=Sportster 33600/Fax V1.1
   
   

2. Update the existing Modem.inf file by appending the

   US Robotics Sportster 33600 V34

   section, as follows:

   [US Robotics Sportster 33600 V34]

   <speaker_on>=m1 <speaker_off>=m0 <hwflowcontrol_on>=&h1&r2 <hwflowcontrol_off>=&h0&r1 <compression_on>=&k3 <compression_off>=&k0 <protocol_on>=&m4 <protocol_off>=&m0 <autodial_on>=ATdt <autodial_off>=ATd

   CALLBACKTIME=10 DEFAULTOFF=compression MAXCARRIERBPS=33600 MAXCONNECTBPS=115200

   DETECT_STRING=ATI3<cr> DETECT_RESPONSE=Sportster 33600/Fax V1.0

   COMMAND_INIT=AT&a3x4e1q0v1s0=0s7=55s2=128<cr> COMMAND_INIT=AT&b1&c1&d2b0x4<hwflowcontrol><compression><protocol> <speaker><cr> COMMAND_DIAL=<autodial><phonenumber><cr> COMMAND_LISTEN=ATS0=1<cr>

3. Change MAXCARRIERBPS to 33600.

For the U.S. Robotics Sportster 28800 v.34 and v.fc modem hardware revision level 2.0, you should select the preexisting entry in the Modem.inf file. The entry is called:

   US Robotics Courier V.32bis

MORE INFORMATION

Aside from the different detection responses, the main difference between the initialization strings of the two modems is that the Sportster 33600 lacks the S47 register. The U.S. Robotics generic initialization string should work for the Sportster 33600 modem if the S47=2 entry does not exist.

Some models may have a different response string based on their firmware version. To verify the response string from your modem, use the Terminal tool to issue the ATI3 command to the modem. This displays the response string. The Modem.inf entry above may need to be modified to match the response of the modem.

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