Common ISDN Application Programming Interface
The Common ISDN Application Programming Interface (CAPI) is an ISDN -compliant standardized programming interface. Using the CAPI interface computer software can be provided for the use of ISDN, without knowledge of the employed, proprietary ISDN card are required.
CAPI was designed in 1989 by German manufacturers ( AVM, Systec, Stoll man) first for the national ISDN protocol 1TR6, then later as a CAPI 2.0 for the European DSS1. Since 1994, CAPI will be further developed by the CAPI Association eV. The specifications of the public are freely available. Implementations exist for different operating systems such as Linux and Microsoft Windows.
From ETSI CAPI 2.0 was first incorporated as " Profile B" in the draft ETS 300 325 and later in the document ETS 300 838: Integrated Services Digital Network (ISDN ); Harmonized Programmable Communication Interface ( HPCI ) for ISDN.
CAPI originally developed for data communication via ISDN. Over time, the specification for the use in the field of voice and fax communication was extended. Due to the trend that pure data transfer is taking place in recent times mainly over IP-based networks, CAPI now also within the scope of voice applications (such as voice mail, IVR, Call Center, Voice Conference ) systems, fax servers, and in combined systems ( is UMS ) used.
The CAPI specification includes in the current version (CAPI 2.0, 4th edition ) includes a plurality of signaling protocols (D - channel protocols ), as customary in Germany DSS1. It is in the OSI layer model between layer 3 and layer 4 to settle, but controls only layer 1 to 3
In addition to the standard signaling protocols for ISDN there are now CAPI specifications for ATM, Bluetooth, GSM and IP Telephony (H.323 and SIP), so that CAPI applications can also be used directly in the current communications infrastructure. Special extensions of CAPI received on protocol-specific properties are defined for ATM for several years. Since 2006 (eg codec negotiation, advanced addressing modes ) are working with the CAPI Association of specification extensions for IP telephony.