This item is listed as "defective" because it cannot be charged via the rear charging port. It can be charged via the USB port. I have confirmed that calls work without issue in a Zoom test. I have confirmed that all buttons function correctly: mute, call, volume up, volume down, and power. The firmware has been updated to the latest version and the announcements are in Japanese (v513). The main unit only. There are signs of use. The app displays a call time of 6 hours and 58 minutes. Battery life is not guaranteed. S/N 216LPN PLANTRONICS VOYAGER 5200 BLUETOOTH: Yes NFC: Yes WIRELESS Headphone Type: Ear-hook type Microphone: Yes Voice assistant function: Yes