Fax Features; Itu Standards For Group 3; Class 1 Fax Standards - Diamond SupraExpress 56e Manual

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This section discusses the following topics:
• ITU S
TANDARDS FOR
• C 1 F
LASS AX
• F F
ONTS FOR
• R
ESOURCES FOR
ITU S
TANDARDS FOR
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 in use today support Group 3.
Group 3 includes three ITU-T 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, technological advances and the proliferation of
faxmodems supporting V.17 has 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. High Speed Communication describes the negotiation process.
C 1 F
LASS AX
Class 1 is the command set used by fax software to control a modem. The fax commands are
invisible to you when you use fax software, and most software automatically determines which class
G 3
ROUP
S
TANDARDS
AXING
F P
AX ROGRAMMERS
G
ROUP
S
TANDARDS
F F
AX EATURES
3
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