Multitech MT4X56, Руководство пользователя

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MultiModemUSB User Guide
MT4X56USB 78
Appendix B - V.90 Support
Introduction
V.90 is the ITU designation for what had formerly been 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/u-law selection and various changes to the AT command documentation.
These new functions are explained in documents that are readily-available on the Multi-Tech web site
in Portable Document Format (PDF) files at http://www.multitech.com/support/manuals/IDCfiles/
manuals.idc . You can download the Acrobat Reader to view PDF files (you may want to bookmark
http://www.adobe.com/prodindex/acrobat/readstep.html before following the “download” link).
For files with a .ZIP extension, you can download PKUNZIP.EXE to extract the zipped files from the
Multi-Tech FTP site at: ftp://ftp.multitech.com/Utiltities/PKUNZIP.EXE. Using your favorite Web
browser, go to http://www.multitech.com/support/V.90upgrades.htm for additional information on
ITU V.90 support and other Multi-Tech products.
V.90 Troubleshooting
1. Check if the modem firmware is the latest. If not, download the latest from ftp://ftp.multitech.com.
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 basic modem/line troubleshooting (check the phone line for noise, try a different line, try
another device on the same line, etc.)