1: Connecting to the headphones for the first time
Check that the headphones are not connected to any Bluetooth device before pairing.
Turn on the Bluetooth function of your mobile device.
For details, see the Owner’s Manual of the Bluetooth device that you want to connect.
Press and hold the 
button for approximately 4 seconds while the headphones are powered off.
button for approximately 4 seconds while the headphones are powered off.The Bluetooth LED lights and then blinks in approximately 1-second intervals as the headphones enter pairing mode.
If the vibration function is on, the neckband vibrates twice when the headphones enter pairing mode. link
The power of the headphones turns on after pressing and holding the button for approximately 2 seconds. Continue pressing the button.
If the Bluetooth LED does not light even when the button is pressed, the rechargeable battery has no power remaining. Charge the battery. link
Select “DENON AH-C820W” from the list of devices displayed on the screen of your Bluetooth device.
When pairing is completed and the Bluetooth connection is established, the Bluetooth LED lights for approximately 2.5 seconds.
If the vibration function is on, the neckband vibrates three times when the Bluetooth connection is established. link
Playing back music on the Bluetooth device.
Music played back on the connected Bluetooth device is output from the headphones.
If the power is on, press and hold the button for approximately 4 seconds to turn the power off before pairing.
The headphones pairing mode is canceled if pairing is not completed within 3 minutes. In this case, press and hold the button for approximately 4 seconds to turn the power off and then pair the devices again.
If you are requested to enter a PIN code (pass key), enter “0000” (four zeros).