This is an instrument system that wirelessly connects a clip microphone and a tuner (using radio waves) for pitch adjustment (tuning). - Tuner: Wireless tuner - Type: Clip microphone, pickup microphone - Model: DW9021 - Connection terminal: 1/4 inch jack - Configuration: Pickup unit (transmitter), tuner connection unit (receiver) - Used by wirelessly connecting the clip microphone and tuner (using radio waves). - Power supply: CR2032 (button battery): 2 (transmitter x 1, receiver x 1) - Used for pitch adjustment (tuning) during instrumental music, wind band, orchestra, and instrument performance. Operation confirmed. The button batteries (2) used during the operation check are included. This item has been stored at home for a long time. Thank you for viewing.