NXD-4F is a USB interface portable phone made by ESTONE Company. It offers USB1.1 interface and built-in 16bit sound card, and is equipped with clear-bimap LCD to support four line display and multiple languages. NXD-4F offers humanistic key operation, mute, redial/dial-back, caller ID, caller statistics, in-call volume adjustment. It also supports personalized ring tone. AU210 has excellent voice quality and rich features. It supports Skype and is an outstanding voice product.