2.2.4 How to Switch Between Data Mode and Command Mode
To switch from data mode to command mode, following methods are available:
(1) The escape sequence can be used if the fourth parameter of AT+CIPCCFG is TRUE. The default escape sequence is +++, and to use this sequence, there should be 1000ms idle period before this sequence and 1000ms idle period after this sequence. Besides, the interval between each + should not exceed 1000ms, otherwise it will be treated as TCP/IP data.
(2) DTR line of serial port can also be used. To use this method, AT&D1 should be set firstly.
Pull DTR line to ground for at least 1 second and then pull up, the module will be switched from data mode to command mode and OK will be returned indicating the module is in command mode.
(3) For TCP client connection, if the remote server closes the connection, the module will be switched back to command mode automatically.
(4) For TCP server connection, if the remote client closes the connection, the module will be switched back to command mode automatically.
(5) If the module is deactivated from PDP context (+PDP DEACT) during data transferring, module will be switched back to command mode automatically.
ATO command can be used to switch the module from command mode to data mode if the connection is active, and CONNECT will be returned again.
2.2.5 How to handle incoming call and short message in data mode
RI pin of serial port will give a 50ms low pulse when a call is coming during data mode. RI pin
will give a 120ms low pulse when a short message is received.

To handle the incoming call or SMS, the module need to enter command mode first (using DTR or +++), and then the module will give the normal unsolicited responses as following:
Grammar Description
RING Incoming call
+CMTI: “SM», 10 New short message