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PORTABLE USB MODEM
Appendix A. V.90 Support
A.1 Introduction
V.90 is the ITU designation for what had been formerly called V.pcm. The ITU
recommendation V.90 was determined at a meeting in Geneva ending February 6,
1998.
V.90 will replace K56flex and other proprietary solutions for PCM connections.
Dual-mode client modem code will be important until all central-site digital
modems are upgraded to V.90 and all interoperability problems have been
resolved. Until that time, the dual-mode client code will provide reliable
connections in K56flex mode to the central-site modems currently deployed.
Your V.90 dual-mode (V.90/K56flex) modem now includes:
• New AT commands,
• New Result Codes in V.90 mode, and
• A-law/µ-law selection and various changes to the AT command
documentation.
A.2 V.90 Troubleshooting
1. Check that the modem firmware is the latest.
2. Try adding one or more comma (,) characters to the dialed number in the
dialing string.
3. Try limiting the speed with the S37 (sets the maximum upstream speed) and
S38 (sets the maximum downstream speed) commands.
4. Perform another basic modem/line troubleshooting (check the phone line
for noise, try a different line, or try another device on the same line).