Dect headset headband headset earhook telephone headset series sennheiser dw transmission modes dect wireless sound mode mono types of headphones headband earhook talking time 12 h standby 100 h features microphone noise reduction volume control signal range outdoor in m 180 m signal range building in m 55 m charging time 1 h material plastic weight 65 g headphone transmission range 150 6800 hz microphone frequency range 150 6800 hz colo