To change connection setting:
1) Slide the compatibility switch located on the side of the device unit it can be properly adjusted.
2) The position of polarity switch is on the right side before factory release as below drawing. To adjust properpolarity switch, make a phone call to your friend and adjust slide switch to the left & right by turns until he can hear your voice more loudly and clearly.
Notices: If you do not properly set the polarity position, the sensitivity of headset microphone will be decreased and dead easily.
3) If you are still experiencing difficulties, the headset configuration may be incompatible with this device.