The BT-89 is microphone, also is speaker. it means it has microphone and speaker function.
Pls try to use it on computer. Open the menu of 8900D, find "REP-M", and set up the "CARRI".
Package Listing:
1 × QYT BT-89 Wireless Hand Speaker Microphone.
1 × USB Charging Cable for Hand Speaker Microphone.
1 × 8-PIN Bluetooth Wireless Adapter/Dongle.
1 × Belt Clip for Hand Speaker Microphone.
1 × English User Manual.
1 × AC Adapter.