Due to the openness of wireless signals, different wireless devices may interfere with each other. Therefore, countries have specific requirements and restrictions for Wi-Fi devices regarding the frequency spectrum, radio frequency (RF) power, security, and more. The Wi-Fi devices shall comply with the requirements of the country or region where they will be sold.
Different countries have different requirements for Wi-Fi channels. For example, the Wi-Fi channels numbered 1-13 are supported by China and Europe (European routers can be used directly in China), while North America supports channels numbered 1-11 and Japan 1-14.
When you apply for a module license, a country code is written into the flash. After the device is started, the country code will be read, and the original API is called to set the channels and related parameters.
(Note: If you choose the wrong country code, the device may not be able to match the network successfully)