The Common ISDN Application Programming Interface (short CAPI) is an

ISDN Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. ...

-conformant standardized software interface. With the help of CAPI,

computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...

software intended for the use with ISDN can be provided, without knowledge of the deployed, proprietary ISDN card. CAPI was designed from 1989 by

German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...

manufacturers ( AVM, Systec, Stollmann). Since 1991, CAPI is being developed further by ''CAPI Association e.V.''

Implementation Implementation is the realization of an application, execution of a plan, idea, scientific modelling, model, design, specification, Standardization, standard, algorithm, policy, or the Management, administration or management of a process or Goal ...

s exist for different

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s, including

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

and

Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

. Through the

ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization operating in the field of Information and communications technology, information and communications. ETSI supports the de ...

, CAPI 2.0 was introduced as standard ETS 300 324 (Profile B). Primarily, CAPI was designed for data transfer over

. The specification has been extended multiple times, thereby it became important to the area of voice and fax communication. Because pure data transfer over IP-based networks is dominant in modern times, CAPI is being used primarily in the scope of voice applications (voice mail, IVR, call center, voice conference systems, etc.), for fax servers and combined systems ( UMS). The CAPI Interface in its current release (CAPI 2.0) supports a variety of signaling protocols ( D channel protocols), e.g.

DSS1 Digital Subscriber Signalling System No. 1 (DSS1) is a digital signalling protocol (D channel protocol) used for the ISDN. It is defined by ITU-T I.411 (ETS 300 102). It supports Bearer Capability, Low Level Compatibility and High Level Compat ...

and FTZ 1 TR 6. The interface operates in the

OSI model The Open Systems Interconnection (OSI) model is a reference model developed by the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems inter ...

between layer 3 and 4, but only controls layers 1 to 3. Besides popular signaling protocols for

, implementations of CAPI for ATM,

GSM The Global System for Mobile Communications (GSM) is a family of standards to describe the protocols for second-generation (2G) digital cellular networks, as used by mobile devices such as mobile phones and Mobile broadband modem, mobile broadba ...

and

VoIP Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as ...

( H.323 and SIP) exist, thus CAPI applications can be used directly on communications infrastructure. Special extensions for protocol-specific features were defined several years ago for ATM.

External links

capi.org

CapiSuite
A Python scriptable ISDN telephony suite with an answering machine. Integrated Services Digital Network