Microsoft LifeChat LX-4000 for Business Selective Sound - The single earpiece provides the ability to handle calls and still hear everything around you. Noise Canceling Microphone - Meetings and conference calls will be more productive as voices clearly cut through even noisy surroundings. Inline Volume and Microphone Controls - Adjust volume or mute on the fly with handy inline controls. And the call indicator light lets people know you're "busy." Plug and Play Simplicity - No software. Just plug it in and you're in business. All Day Comfort - An ergonomically influenced earpiece and a 270-degree adjustable microphone provide all-day comfort.