Call anyone else using SDK (or any SIP compliant services) anywhere in the world totally free. Call Waiting and 3-way Calling make it easier to stay in touch. Call missed, or on a call? Dont worry, free voicemail is included. Call regular phones with SDK Dial Out and save big. Get 30 min. free for domestic U.S. calls when you sign-up. Exchange instant text messages with your online contacts, including Google(TM) Talk users. Exchange files and photos quickly and easily, plus preview your email in your free Webmail account that you will receive. Tell your friends. Use the built-in Invite feature to tell your friends to get SDK. Free For All - EarthLink access is NOT required. PS: Check out SDK VoIP Home Phone Service: Use SDK to make calls to regular phones and apply the minutes to your Voice account. Calls made to your home are always free. Version 3 enhances user interface and sound quality. SIP SDK includes SIP activeX , SIP OCX , SIP DLL , SIP Lib and SIP Cab, so you can use the one you like the most. It is really easy to incorporate SIP controls in your web pages and/or applications. Sample source codes are available to download. SIP SDK can also be used to develop softphone for MS Windows Mobile based Pocket PC and Hand-Held devices. It delivers superior voice quality by integrating advanced digital voice processing features including acoustic echo cancellation, noise cancellation and adaptive jitter buffering. For more details, please visit the features link.