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.
TAC I/A Series
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.