Premium Features: 4 Lines,Call Recording,Hold / Unhold ,Transfer (Xfer),DND (Do not Disturb),Redial,Mute,Auto accept call,NAT/Firewall support STUN server Support ,ICE Support,Debug Mode (SIP message log),Codec Supported,G729, G711 u, G711 a, G722, GSM, iLbc, Speex/ 8000, Speex/16000 , Speex / 32000,Codec selection and Codec Quality Control (Bandwidth control),Silence Suppression,Echo Cancellation Uses NEW RFC 3261 compliant stack,DTMF (RFC 2833),RFC 3951: Internet Low Bit Rate Codec (iLBC),Proxy Settings,Registration Timeout Acoustic Echo Cancellation,Packet concealing,Packet Lost Concealment (PLC),Comfort Noise Generator (CNG),Resampling,Balance Display Credit time display. Basic Features: Customized skin interfaces ,Call timer ,Last Number Redial ,Touch Tone ,Address Book ,Micro Phone Volume Control ,Speaker Volume Control ,Work with any full-duplex sound card ,Auto-configuration of settings for easy deployment