GN NETCOM 7550-09 Jabra 550 Landline Telephone Accessory HD Voice - High quality audio for crystal clear conversations Enjoy high-definition sound with HD Voice and get crystal clear, intelligible communication Omni-Directional Microphone - Jabra audio devices with Omni-directional microphones pick up your voice to get life-like natural sounding conversations in environments with low or no background noise Peak Stop - Peak Stop technology immediately removes potentially harmful loud sounds or tones before they reach your ears and keeps the sound level witching the safe range to protect your hearing