Serial Programming - upload.wikimedia....

Appendex A:Modems and AT Commands
9.9 S-Registers
See S-Registers 51
9.10 Advanced Features
9.10.1 Introduction
Modern consumer modems provide a number of additional features which were originally
uncommon for a modem, but became standard features over time. This section provides an
overview about how to program these features.
9.10.2 Fax Class 1
9.10.3 Fax Class 2
9.10.4 Voice Services
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http://en.wikibooks.org/wiki/Serial%20Programming%2FModems%20and%20AT%20Commands%
2FS-Registers
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