ZyXEL Communications U-90E, Руководство пользователя

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U-90E Data/Fax Modem
Basic Modem Operation
4-1
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
The U-90E communicates asynchronously with computers using
AT
commands.
AT
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
them. A command statement always begins with the letters
AT
or
at
. 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
In order to issue an
AT
command statement, you first need to run a communication
program such as the Microsoft Windows “Hyper Terminal” program. This program
provides a simple method to manually enter
AT
commands so you can do such things as
“customize” the settings of your modem, or store commonly used phone numbers.