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COMSPHERE 3821Plus Modem
4-2 February 1998 3821-A2-GB20-30
To enter online Command mode while in Data mode,
enter the following sequence:
TYPE: +++
Use the O command to return to Data mode from
online Command mode. Enter the following command:
TYPE: ATO
PRESS: Enter
Command Guidelines
Review the following guidelines before using any
AT Commands.
• The escape sequence (+ + +) is used to enter online
Command mode from Data mode.
• The asynchronous character format for the
AT command set must be one of the following:
— 8 data bits + no parity + 1 stop bit.
— 7 data bits + no parity + 2 stop bits.
— 7 data bits + parity + 1 stop bit (parity can be
odd, even, mark, or space).
• All commands except A/ (repeat last command) and
the escape sequence (+ + +) must begin with the
characters AT and end by pressing the Enter key.
The AT (or at) prefix clears the command buffer
and matches the modem speed and parity to that of
the DTE. Commands can be upper- or lowercase,
but the modem will not recognize mixed case
prefixes (At or aT).
• Commands can be entered one at a time or in
strings. Strings can have up to 40 characters after
the AT prefix. You can use spaces, hyphens (-), and
parentheses ( ) as fillers to make the commands
easier to read; the modem ignores these fillers and
they are not counted among the characters which
make up the command string. Commands must be
entered on one line and end with the carriage return
character (Enter key).
• Commands shown with the suffix n have several
options associated with them. For example, in the
Ln command, L1 sets the speaker volume to Low
and L3 sets the speaker volume to High. Omitting
the suffix has the same effect as using a zero suffix;
for example, ATX is equivalent to ATX0.
• The A/ command (without pressing the Enter key)
causes the modem to repeat the last command
entered.
• Valid commands are acknowledged with numeric or
word result codes (unless the result codes have
been disabled using the Q1 command).
Appendix B lists all available result codes with
numeric and word equivalents.
AT Command List
AT commands are issued from an asynchronous DTE,
such as a PC, and control the modem’s operation and
software configuration. AT commands are only applicable
when the DTE Dialer Type configuration option is set for
AT. (See &Mn and &Qn commands.)
AT commands are entered while the modem is in
Command mode and use the following format:
TYPE: AT Xn
Where: X is the AT command and n is the specific
value for that command.
PRESS: Enter
Table 4-1 lists all AT commands supported by the
3821Plus modem. The Async Dial factory default is listed
in bold.
Reference to particular country codes in this guide is
not an assurance that the modem has been approved for
use in that country. Consult your sales representative.
Not all commands are valid in all countries. See
Appendix H.