Western Telematic MT5634 - Manual (Page 6)

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MT5634 Modem; AT Command Set
You can issue several commands in one line, in what is called a command
string. The command string begins with AT and ends when you press [Enter].
Spaces to separate the commands are optional; the command interpreter
ignores them. The most familiar command string is the initialization string,
which is used to configure the modem when it is turned on or reset, or when
your communications software calls another modem.