Free voip sip sdk software for windows

3CX VOIP Phone is a useful and free VOIP / SIP phone. Use your PC as a phone. Works with any SIP / VOIP provider/ phone service. Use instead of the soft phone provided by your VOIP provider which locks you into their VOIP phone service.
Easy to use interface includes dial pad and buttons to transfer or forward a call. Set-up conference calls with a few mouse-clicks. Includes call log, phone-book, call status & statistics and more. Available in English, German, Spanish, French & Portuguese.
3CX VOIP Phone for Windows also functions as a client for 3CX Phone System for Windows, a software-based VOIP PBX that completely replaces a traditional proprietary phone system. More information on http://www.3cx.com/phone-system.
Main features:
- Integrated phone book (allows you to assign caller ID to a name)
- Supports several SIP profiles
- Displays caller ID
- Individual ring tones (per caller)
- Drag & drop handling
- Call log
- Incoming calls: identify, accept, reject or ignore
- Record phone calls
- Multiple calls (HOLD)
- Terminal portability (TP)
- Call transfer (ECT)
- 3 party conference (3PTY)
- Call diversion (FORWARD)
- Call deflection (CD)
- Call completion (CCBS and CCNR)
- Message Waiting Indication (MWI)
- EarlyB3Connect (tones from trunk line)
- Keypad
- VoIP support for SIP connections
- Support G.711 (A-Law and u-Law), G 726, GSM, iLBC and Speex codecs.
- STUN support for NAT/firewall traversal.
- Search using ENUM
- Installation provided as MSI for easy deployment

System Requirements: sound card, microphone, internet connection

ZOIPER is a new generation SIP and IAX softphone compatible with the Asterisk platform as any other IAX or SIP capable VOIP system.
Main features:
- SIP + IAX/IAX 2 protocols
- STUN support
- STUN server per account
- Echo cancellation
- DTMF tones sending
- Support for multiple audio devices
- Automatic user registration
- Call transfer, Hold function
- Codecs: GSM, ulaw, alaw, speex, ilbc, Adaptive
- Call history
- Address book
- Quick dial panel
- Optional Automatic pop-up window for incoming call
- Always on top
- Call logs
- Voice mail message information
- Account password encryption
- Upgrade notification
- Jitter Buffer
- Adjustment of audio device
- Codecs priority
- Portable storage compatibility
- Multilanguage support
ZOIPER can also be re-branded and you can choose one of the three types of re-branding:
- Basic - colours, name and logo to your choice
- Re-branding with additional development - e.g. changing the language; adding, disabling, removing menus, options, buttons, adding functionalities;
- Complete - you can go for complete change of the interface and functionality.
System requirements:
- Pentium II 300
- 256 MB RAM
- Sound card: 16 bit

• Supports several SIP profiles
• Displays caller ID
• Shows personal call log/history
• Incoming calls - identify, accept, reject or ignore
• Put calls on hold (HOLD)
• Transfer calls with the click of a button (ECT)
• Diverts calls to voice mail
• BLF - change status option
• Shows extensions, lines and queues in one or multiple screens
• Message Waiting Indication (MWI)
• TAPI driver for integration with Microsoft
• Keypad with intuitive interface
• VoIP support for SIP connections
• Support G.711 (A-Law and u-Law), GSM, iLBC and Speex codecs
• STUN support for NAT/firewall traversal
• Installation provided as MSI for easy deployment
• Integrated phone book (allows you to assign caller ID to a name)