Some older modems will successfully connect with the USRobotics 5686 series V.92 modems on the first call, but will fail to connect on subsequent attempts.
USRobotics 5686 series V.92 modems
The V.92 protocol must be disabled when using these modems with older modems.
To disable the V.92 protocol on the USRobotics 5686 series modems:
Enter the following setup string in addition to the string specified in the referenced bulletin, before saving the settings: AT +PIG=1 +PMH=1 +PQC=3
Refer to Bulletin 00-47 for additional information.