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. Work ...

-conformant standardized

software interface In computing, an interface is a shared boundary across which two or more separate components of a computer system exchange information. The exchange can be between software, computer hardware, peripheral devices, humans, and combinations of these ...

. With the help of CAPI, computer software intended for the use with ISDN can be provided, without knowledge of the deployed, proprietary

ISDN card Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous Digital data, digital Transmission (telecommunications), transmission of voice, video, data, and other network services over the digitalised circui ...

. CAPI was designed from 1989 by

German German(s) may refer to: * Germany (of or related to) ** Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **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, or execution of a plan, idea, model, design, specification, standard, algorithm, or policy. Industry-specific definitions Computer science In computer science, an implementation is a real ...

s exist for different

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...

s, including

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, w ...

and Microsoft Windows. Through the ETSI, 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 Interactive voice response (IVR) is a technology that allows telephone users to interact with a computer-operated telephone system through the use of voice and DTMF tones input with a keypad. In telecommunications, IVR allows customers to interac ...

, call center, voice conference systems, etc.), for fax servers and combined systems (

UMS UMS may refer to: * Ulnar–mammary syndrome * Underwriting Management System, for automated Insurance Underwriting * Unfederated Malay States * Unified Messaging (System, Server, or Service) * Uniform Mark Scheme * United Mexican States (officia ...

). The CAPI Interface in its current release (CAPI 2.0) supports a variety of

signaling protocol A signaling protocol is a type of communications protocol for encapsulating the signaling between communication endpoints and switching systems to establish or terminate a connection and to identify the state of connection. The following is a list ...

s (

D channel D channel (delta channel) is a telecommunications term which refers to the ISDN channel in which the control and signalling information is carried. The bit rate of the D channel of a basic rate interface is 16 kbit/s, whereas it amounts to 64 kb ...

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 FTZ 1 TR 6 (or 1 TR 6) is the standard for the obsolete German national digital signalling protocol (D channel protocol) used for the ISDN. It has been superseded by DSS1 but is still in use on some lines and private exchanges. 1 ...

. The interface operates in the

OSI model The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...

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 standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation ( 2G) digital cellular networks used by mobile devices such ...

and

VoIP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet t ...

( 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