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.