Dect headset earhook telephone headset headband headset series sennheiser dw transmission modes dect wireless sound mode mono types of headphones headband earhook talking time 12 h standby 100 h features volume control signal range outdoor in m 180 m signal range building in m 55 m weight 50 g headphone transmission range 150 6800 hz microphone frequency range 300 3500 hz call function muting type of fitting on ear manufacturer specific f