Common ISDN Application Programming Interface
The Common ISDN Application Programming Interface ( CAPI ) is an ISDN -compliant standardized programming interface . With the help of the CAPI interface, software for the use of ISDN can be provided without knowledge of the manufacturer-specific ISDN card used .
CAPI was designed by German manufacturers ( AVM , Systec, Stollmann) from 1989 , initially for the national ISDN protocol 1TR6 , and later as CAPI 2.0 for the European DSS1 . CAPI has been further developed by the CAPI Association eV since 1994 . The specifications are freely available to the public. There are implementations for various operating systems such as Linux and Windows .
CAPI 2.0 was initially adopted by ETSI as "Profile B" in draft ETS 300 325 and later in document ETS 300 838: Integrated Services Digital Network (ISDN); Harmonized Programmable Communication Interface (HPCI) for ISDN.
CAPI was originally developed for data transmission via ISDN. In the course of time, the specification was expanded for use in the area of voice and fax communication . Due to the recent trend that pure data transmission has mainly taken place via IP-based networks, CAPI is now also used in voice applications (e.g. Voicemail , IVR , call centers , voice conference systems ), for fax servers and in combined systems ( UMS ).
The current version of the CAPI specification (CAPI 2.0, 5th edition) includes a large number of signaling protocols ( D-channel protocols), for example the DSS1 used in Germany . It is located in the OSI layer model between layer 3 and layer 4, but only controls layers 1 to 3.
In addition to the common signaling protocols for ISDN, there are now also 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 communication infrastructures. Special extensions of CAPI, which deal with protocol-specific properties, have been defined for ATM for several years. The CAPI Association has been working on specification extensions for IP telephony (e.g. codec negotiation, extended addressing types) since 2006 .
See also
Web links
- Official CAPI website (English)
- A Python scriptable ISDN telephony suite with answering machine (English)