PC-to-PC and PC-to-phone operation; Driver built-in, plug and play; USB 1.1 compatible; No need sound card; No external power required; Complies with H. 323, MGCP, SIP protocol; Echo cancellation, noise reduction; Application support: Skype, Netmeeting /Messenger, Sjphone, Mediaring, Net2phone, Dialpad, Etalk, X-PRO, X-PRO Vonage, Firefly, Eyebeam and so on; Full duplex communication; Support Skype speed-dialing function; Key-in tone function.