After connecting correctly, install the "Bluetooth Smart Control" app on the Android mobile phone, search for Bluetooth devices and connect with a pairing password of 1234. Long press the gray box in the interface to add serial port commands, enter the name and content of the command (A00101A2 is to open the relay/A00100A1 is to close the relay), and select to send it in hexadecimal format. Then, click the corresponding box to control the switch of the relay, You can also download other Bluetooth apps from the app store to control by sending commands.