SIPTAPI is a TSP (TAPI service provider) for Microsoft Windows. SIPTAPI allows you to initiate phone calls from within any TAPI application (click2dial). SIPTAPI is not a SIP phone, it is a SIP based "3rd party call controller" which commands your existing SIP phone to call a certain number. SIPTAPI uses the SIP protocol for call control, thus it can be used with any SIP proxy/PBX (Asterisk, Openser ...) and any SIP phone (softphones, hardphones) which support call transfer (SIP REFER request method).

There are two different versions of the SIPTAPI - a free version (GPL license) and a commercial version. The free version is rather simple - it supports only a single line (one SIP account) and outgoing call initiation. This is usually sufficient for a typical desktop working place. The commercial version supports multiple lines (multiple SIP accounts) and thus can be used on Windows terminal servers (e.g. Citrix, ...) too. Further, the commercial SIPTAPI also supports incoming call indication.

SIPTAPI is developed by IPCom GmbH, main developer is Klaus Darilion.

The website of SIPTAPI is at http://www.ipcom.at/en/telephony/siptapi/.