The BT41 and BT50 are two different USB bluetooth adapters for use with USB port supporting desk phones. These adapters (dongles) can be used to connect the desk phone with various bluetooth enabled devices such as cordless headsets.
Differences
Key differences are that the BT41 is comparable to a generic bluetooth adapter while the BT50 can be pre-paired with a bluetooth audio device and is detected by a Yealink phone as a USB headset.
Updating
As with all upgradeable devices always ensure that the deskphone and adapter are updated to the latest firmware before configuring them.
BT41 will be automatically updated via the desk phone running the latest firmware. BT50 is updated via YUC.
Pairing
The BT41 pairing is done via the desk phone interface. The pairing is managed by the phone.
BT51 pairing is managed via Yealink USB Connect (YUC) desktop software. YUC can be downloaded from the Yealink support website. Any pairing done on the BT50 sticks with that dongle and so can be moved to another phone or PC keeping its association with the audio device. This is why it's detected as a USB headset when attached to a supported desk phone.
