Plantronics M22 amplifier brings superior sound-quality and acoustic protection to your telephone. As well as providing compatibility with those telephones that do not allow direct connection of headsets it offers a range of additional features to enhance the sound quality of your phone conversations. Plantronics SoundGuard Plus™ technology ensures loud tones are quickly reduced to more comfortable levels and ensures that the normal, human voice remains natural and unchanged, for face-to-face clarity of communication. Plantronics Call Clarity™ technology uses electronic signal processing to reduce phone noise and maintain constant volume levels, as set by the user. This ensures all conversations are held at a comfortable and consistent level, regardless of the loudness of the incoming call.