The USB Phone is voice comunication terminals over the internet. It is a different way of comunication from traditional telephones. It connects directly to PC through the USB port. With DSP chipset set inside. its sound is very clear. PC to PC is free of charge. You can make calls from PC to regular phone when the internet is connected with PSTN network by gateway. It can work with cable and Dial-up internet, Broadband and LAN connections.It is especially suitable for those who make long-distance calls frequently. Easy to use, easy to set up. The best of all,it saves money   Functions: PC to PC, PC to Phone dialing capabilities Easy to install USB plug and play Full duplex audio, echo cancellation Compatible with all popular VoIp soft service such as Bitcall,Netmeeting,MSN,Netphone Rings on an incoming call(Built-in speakerphone ring) Without the need for drivers PC sound card not required Speaker phone Volume adjustable(increase and reduction keys) Mute key with LED Led indicates USB phone working state Electric Parameter: Conformity to USB Audio Device Release 1.0 Conformity to USB HID version 1.0 Valtage:4.5-5.25V DC The network system requiry: CPU: Pentium200/64MB Ram/100MB Operation system: Microsoft Windows98/SE/ME/2000/XP Internet Condition: LAN, Cable Modem, XDSL, ISDN, or Dial-up Modem