Additional handset KX-TGA681AZB is available for purchase separately. This unit can take up to 6 handsets. Noise reduction. Reduce the background noise of the other party. Suppresses background noise around the caller while simultaneously enhancing their voice, making it easier to hear. Incoming call block. Night mode. Incoming Call Block and Night Mode functions allow you to customize your phone so that it only rings when certain people call or stays silent at pre-set time. Advanced answering system. Catch answering machine calls whether you are at home or away.