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Questions Related to Network

What are the reasons why modules fail to register to the network after starting up?
1) If AT+CPIN is used, check if the module recognizes the SIM card.
2) Check if the SIM card PIN code is required.
3) Check if the SIM card is working.
4) Check if the SIM card has the roaming service, and if it uses the local network or not.
5) Check if the RF antenna is properly connected.
6) Check the RF signal quality with AT+CSQ.
7) Check the working frequency band and working mode if you use AT + CBAND? and AT + CFUN?.
How do I use the hot plug function of the SIM card?
1) Design the SIM card deck of 8 pins based on the HD instruction and check the SIM_PRESENCE pin of the connected modules.
2) Start the SIM card detection function by AT command.
For example:
AT + CSDT = 1 //Start the SIM card detection function.
AT + CSMINS = 1 //Start the plug-in state report of the SIM card.
For details, please refer to the ATC manual for details.
Why the module returns "+creg:0,3" when sending AT+CREG?

"+ CREG:0,3" means the registration is declined, which may be caused by no available PLMN (SIM card cannot be used) or no SIM card with the roaming service.

How do I obtain and cut off the information to neighboring cells?
Open the engineering mode: AT + CENG = 1,1, and perform read command: AT + CENG?
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