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Step1. Enter the setup state
Press and hold the key first, and then power on. After power on, keep the key pressed until the "BP" sound is heard for 3 times and then release it (the "BP" sound will be heard once per second) to enter the setting state, and the indicator light will flash slowly;
Step2. Initialization
Press the Call key once to execute the factory initialization operation, and complete and exit after a long sound of "BP +";