H91N Encore headsets are equipped with an SES (Sound Enhancement Systems) tone control switch. This switch is conveniently located just below the ear pad on the headset. The SES switch allows you to tune your Encore headset like you would tune your stereo, adding more base or treble to enhance your listening pleasure. With an Encore H91 headset your phone conversations are easily understood and more pleasant, plus the H91 is so light and comfortable it is preferred by the most discriminating professionals. Monaural ear pad can be easily switched from right to left ear. Voice tube microphone assures world-class sound quality. Comes with Plantronics Quick Disconnect feature which acts as an on-hold function–walk away from your phone while still wearing your headset. The Encore H91N combines the features and performance of the Plantronics Encore H91 headset with noise-canceling microphone technology to reduce the transmission of background noise in the workplace.