Using At Commands - Samsung N640 User Manual

In command mode, you can call by using AT commands and communicate with
others by connecting to other modems. You can call this status Data mode or On-
line mode. In data mode, You can't use any AT commands except the +++
command, which has +++ at the head.
If you stop communication and disconnect the phone, the Fax modem will run in
command mode again.
Using Command Mode during Communications
Sometimes, you have to use AT command while you're communicating with
others via modem. In this case, you can use +++ command for AT command
without hanging up your telephone. Pressing '+' three times makes fax mode
change to command mode. Of course, the telephone is not disconnected. (Don't
enter Enter key after input +++)
If you want return to Data mode from command mode, you only have to input ATO
and press the Enter key to start the communications again.

Using AT commands

AT commands can be used in the following way. There's no difference between
capital letters and small letters, and all commands should include 'AT' as a prefix
except ones, which includes 'A/' instead.
Also, Carriage Return saved in the S3 register should be entered in order to sign
the end of the command.
Example: ATDT 123-4567
Display the result value
After entering AT commands, the result value is displayed on the screen.
46 Using the Modem
Connection may be lost depending on the server.
The mode can not be transfored from the command mode to
data mode depending on the server.
AT command Press Enter key
Press Enter and the model dials to 123-4567