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U-90E Data/Fax Modem
Chapter 4
Basic Modem Operation
This chapter covers the basic commands and techniques involved in modem operation. In
many cases, this is the only information you will need in order to use the communication
software, and to start making connections with your modem.
4.1
Understanding AT Commands
AT
AT
The U-90E communicates asynchronously with computers using
commands.
commands are used to configure and control your modem. Commands are usually sent to
the modem by way of communication software, but can also be entered manually by the
user with the computer keyboard.
Command statements must be written in a specific form for your modem to recognize
AT
at
them. A command statement always begins with the letters
or
. One or more
commands and the <Enter> key then follow it.
AT
commands can only be issued when your modem is in "command mode" or "off-line."
Once your modem has established a connection with another modem it is said to be "on-
line" or in "data mode." In this mode, the characters sent to your modem by your computer
are transmitted to the remote modem rather than being interpreted by your modem as
commands.
4.1.1 Using the Windows 95 Hyper Terminal Program
AT
In order to issue an
command statement, you first need to run a communication
program such as the Microsoft Windows "Hyper Terminal" program. This program
AT
provides a simple method to manually enter
commands so you can do such things as
"customize" the settings of your modem, or store commonly used phone numbers.
Basic Modem Operation
4-1
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