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Fax Features







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[Table of Contents]
[Introduction]
[Communication Standards]
[Using AT Commands and Result Codes]
[Dialing]
[Answering]
[High Speed Communication]
[Solving Problems]
[If You Need Help]
[AT Commands]
[S Registers]
[Result Codes]
[Glossary]


This chapter discusses the following topics:

ITU Standards for Group 3
Class 1 Fax Standards
Fonts for Faxing
Resources for Fax Programmers


ITU Standards for Group 3
The International Telecommunications Union (ITU) is an international standards committee. Their world wide communication standards (also known as protocols) make it possible for devices such as fax machines and faxmodems to communicate with each other.

Group 3 specifies image resolution, complex data compression, and other features such as connection rates. The majority of fax devices currently in use support Group 3.

Group 3 includes three ITU protocols that allow fax communication at specific connection rates: V.17, V.29, and V.27ter. V.17 defines communication at various speeds up to a maximum of 14,400 bps. V.29 defines speeds up to 9600 bps, and V.27ter defines speeds up to 4800 bps. Most fax machines today communicate at 9600 bps. However, technological advances and the proliferation of faxmodems supporting V.17 have made 14,400 bps fax connections more common.

A connection begins when your modem answers a call from another modem, and ends when either modem disconnects. Because of negotiation, the process of making a connection might take several seconds after dialing. The High Speed Communication section describes the negotiation process.

Class 1 Fax Standards
Class 1 is the standard command set used by fax software to control a modem. These fax commands are invisible to you when you use fax software, and most software automatically determines which class to use.

If you need help installing your fax software, refer to your fax software manual.

Fonts for Faxing
To ensure the best quality fax output, it is important to use both screen and printer fonts, and if applicable, to also use Adobe Type Manager (ATM)® or TrueType®. A common problem is selecting a font that is built into your printer for which you have a Screen font, but not a Printer font. The type looks fine on your screen, but will be faxed in block letters because it uses the Screen font to create each character. The solution is to use a font with both Printer and Screen fonts or to obtain the printer font you need.

Resources for Fax Programmers
Available fax software should provide all the fax functions most users need. However, if you are an advanced programmer and want to write fax software, you can obtain information about fax commands by searching International Telecommunications Union (ITU) and/or Telecommunications Industry Association (TIA) web sites, or from the following source.

The telephone number is (714) 261-1455. Additional phone numbers are: 1-(800) 624-3974 in the U.S. and 1-(800) 854-7179 outside the U.S.

The PC-specific fax driver and utilities (for both DOS and Windows) are available for license by faxing a request to Developer Relations at Thought Communications, Inc., The fax number is (408) 452-1011. Request the Fax Application Programming Interface (FAPI).

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