User's Manual

Chapter 2 AT COMMANDS:
DATA MODEM
Guidelines for Using AT Commands
The modem is programmed with AT commands from the data terminal
equipment (computer, PC or terminal) and thus also receives instructions to
cover automatic dialing. The communications or fax software will carry out
most of these operations for you, so that in general circumstances you do not
need to have a detailed understanding of the commands which are described
below.
The modem must be in Command mode before it can accept commands. In
this condition, all the characters sent from the computer are interpreted as
commands and, where appropriate, confirmed by a modem message on the
screen. When a connection is set up to a remote modem, the modem will
switch to data mode and transfer all the characters it receives to the other
party.
The modem can be switched from an existing connection, back into the
command mode, by using the Esc Sequence (+++), without breaking off the
connection to the remote modem. In this status, any commands which are
entered will not be transferred to the remote modem.
The modem is activated by AT commands, the subsequent value of which will
modify the form of the command. Modem messages provide information on
the form of the commands.
In the Hayes Command Set, commands are entered by the character
sequence AT (at) and can also be entered as a list of commands with or
without spaces between the individual commands. The “Backspace” key is
used for deleting. Commands can be entered in upper-case or lower-case, but
all characters for a given command must use the same case. In the command
mode, the modem automatically recognizes data frames and data speed.
=> AT commands can be transferred to the modem at the following data
speeds: 115 200, 57600, 38400, 19200, 9600, 4800, 2400, and 1200 bps
Examples of Command Syntax:
ATX3<CR>
ATQ0<CR>
ATDT12345<CR>
Individual commands ending with the <CR> Enter key, can be entered in a
different manner with the same effect, by inserting as many spaces as you
need, to make the command easier to visualize
ATX3QODT12345<CR> or:
AT X3 Q0 DT 12345<CR>
AT COMMANDS: DATA MODEM 2-1