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PN 88300150
3.1
Introduction
The MT2834MR incorporates a microprocessor-based Command Mode, which allows you to use your
computer keyboard or communications software to interact with your modem. When your modem is in
Command mode, you have access to a complete communications system which allows you to use a
number of features including the basic AT command set described in this chapter. The basic AT
command set allows you to type phone numbers for automatic dialing without a telephone set, configure
various modem options and monitor phone activity. Beyond the basic AT commands and capabilities,
your modem can also perform advanced features such as error correction, data compression, speed
conversion and more. Some of those features are covered in Chapter 5 of this manual.
This chapter explains Command mode, and shows you how to use each of the basic AT commands.
The MT2834MR AT commands and responses are compatible with all systems and software that have
been programmed for automatic, software-controlled autodialing using the standard AT command set.
The MT2834MR also provides V.42 error correction (using the MNP or LAP-M protocols), data
compression (using the MNP) Class 5 and V.42bis protocol), speed conversion, and remote
configuration. These advanced features are described in either Chapter 5 of this manual.
3.2
Typographic Conventions Used in This Manual
It is important to point out the difference between the letter O and the number 0. Both of these characters
will be used in the MT2834MR's commands. As you can see, the letter O is "fatter" than the number 0.
We do not use the overstriken 0 to symbolize zero in this manual.
The Carriage Return and Control keys are used in many of the MT2834MR commands. Some keyboards
label the Carriage Return key as ENTER, others use the word ENTER, and still others use an arrow
pointing down and then left. The symbol <CR> is also commonly used. In this manual, we symbolize
Carriage Return with the word ENTER, and will usually use the phrase "hit ENTER" to instruct you to
press the Carriage Return key.
We symbolize the Control key with CTRL. For example, Control X, which is accomplished by pressing the
X key while holding down the Control key, is written as CTRL-X.
3.3
Functional Modes
The MT2834MR can be in one of two functional modes. These are "Command mode," and "On-Line
mode." (There is also an in-between mode, "Wait-For-Carrier," where the modem is out of Command
mode but not yet really On-Line.) When the modem is initially powered up, it is in Command Mode, and is
ready to accept commands from your keyboard or software, and respond to any Command Mode
commands (described later).
The MT2834MR enters On-Line mode after dialing and making a connection with another modem, and
then detecting a valid carrier signal tone. If no carrier signal is detected within a certain time, the modem
abandons the call and re-enters Command mode.
Once On-Line, the modem exits On-Line mode if the carrier signal is lost or intentionally dropped. When
this happens, the modem hangs up and re-enters Command mode.
The MT2834MR can exit the On-Line mode without losing the carrier signal. This is accomplished by
typing certain "escape" characters while on-line, which brings the modem back into Command mode
without terminating the connection.
The MT2834MR can also enter On-Line mode without going through the dialing process, by typing either
the O command or the A command. This is explained later in this chapter, as are all of the MT2834MR's
commands.
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