Pairing (registration) is an operation that is required in order to connect a Bluetooth device to the earphones. When using Bluetooth for the first time, you need to pair the earphones and your Bluetooth device so they can communicate with each other. Once a Bluetooth device has been paired with your earphones, pairing does not need to be performed again for future Bluetooth connections with that device.
Pairing needs to be done again in the following cases.
When 9 or more devices have been paired with the earphones
These earphones can store pairing information from a maximum of 8 devices. When 9 or more devices are paired, the new pairing information overwrites the oldest pairing information in order from the oldest information onwards.
Multiple Bluetooth devices cannot be played back at the same time.