Remember the following important points about what we learnt in this chapter:

• AT commands, also known as the Hayes command set, are simple text-based commands that are used to instruct and control modem-based communications systems.
• The GSM module has multiple GND pins. Always connect the appropriate pin. Connecting a wrong GND pin will result in overheating and damage.
• Most GSM modules are rated between 1-2 Amps. However, 1.5 Amps power supply is often fine for normal use.
• After inserting a SIM card into the GSM module and powering it up, wait until the NTW LED starts blinking at regular intervals of 3-5 seconds.