When the outdoor siren already has a pairing record, you need to unpair the device on APPs, then press and hold the pairing button (you need to take apart the back lid to press the pairing button) on the device for 5 seconds. When you see the green light flashing continuously, the outdoor siren has entered pairing mode, and you can operate the app to connect to the RBF network. Another method is to scan the QR code on the outdoor siren to connect to the network.