Common at Commands include (smslib)

Atz soft reset modem.
At & K0 disable traffic control.
At & K3 uses the RTS/CTS stream control.
At & W0 saves the current settings to the factory settings configuration file 0 written to the permanent storage of the modem.
At & y0: When the modem is powered on, it automatically calls factory settings 0. This ensures that the preset parameters are restored each time the modem is powered on.
Atdn dialing, where N is the phone number. It must be the last command in the command line. After the ATD command disconnects the modem, it dials according to the input parameters to establish a connection.
++ Exit character. Switch the modem from the online status to the command status without interrupting the data connection.
ATA response. It must be the last command in the command line. The modem continues to execute the Connection Program in the response mode. After switching the carrier with the remote modem, it enters the connection status. If no carrier is detected, the modem will be suspended. During the connection, any letter entered through DTE will interrupt this command.
Enable the modem to be mounted at ATH0
Ate0 close command character echo
Ate1 open command character echo
Factory settings for AT & F modem Adjustment
Ats0 = N: Set the modem to automatic response. When the modem detects the ringing tone on the line, it starts counting. When there are n consecutive ringing tones, the modem automatically picks up the machine and responds to the call.
Note: after each at command is entered (except ++), + CHR (13) is input, that is, the "enter" key is used to send the command. If it is sent in hex format, press enter and line feed code at the beginning and end of the command. For example:
ATE0----0D 0a 41 45 30 0d 0a
Common responses include:
The OK response is correct.
Error code.
Ring.
Busy is busy.
No answer has no response.
Connect 9600 dialing successful.
No carrier is mounted to the other party.
No dialtone dialing has no response.
Dial phone:
When "ATD" + phone number + CHR (13) is sent, the modem starts to dial up. It takes some time to dial up, during the dialing process, you can constantly read the status of the modem's CD indicator. When the phone is switched over, the CD indicator will light up. And return the "Connect + baud rate" information.
If the modem of the other party cannot be detached, "No dialtone" is returned, and the CD indicator is off.
If the recipient's phone number is busy, "busy" is returned ". The CD indicator is off.
Send data through MODEM
After the phone is dialed, the modem can automatically transmit the data information in the buffer zone sent by the serial port to the modem of the other party through the telephone line. The Modem of the other party is transmitting the information to a device, modem also sends the information returned by the device to the buffer zone of a computer. The whole process is completed automatically, so you don't have to worry about whether your information can be sent out.
Call
After the phone is dialed, the modem no longer receives the AT command. To make it return to the command status, it must send the "++" message to bring the modem back to the command status, then, send "ath" + CHR (13) to stop the call.

Example: (the serial port debugging assistant is used as an example)

I have a built-in modem in the serial port com3. Use the serial port tool to open this serial port.

Enter atd87650467 Temperature

Note: Press enter. Do not press more.

Then click "manually send"

You will hear the sound of modem burst (of course you need to connect to the telephone line)

In this way, you control the modem to dial the number 87650467.

For example, if you connect a modem on the terminal 87650454, open the serial port in the same way and enter ATA and click "manually send ". Hey, so that everyone will be connected. Then you can enter any character and click the send button to chat. Interesting. Let's see what new things you can use to entertain yourself. For example, in online games, it's good to have a game player.