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Appendix B: The Applications Interface CAPI 2.0
As early as 1989, ISDN manufacturers began develop-
ment work on a standard interface for the rapidly expanding
ISDN market. The first version of CAPI concentrated on
the German national ISDN protocol 1TR6, since an
international standard for ISDN protocols was not yet
available. In 1990 development was complete, and a
CAPI Working Group was formed by manufacturers of
ISDN application and hardware, large-scale ISDN users,
user groups and the German PTT, at that time DBP
Telekom. Common ISDN API Version 1.1 represented
a major step towards opening up the national ISDN
market in Germany. Today all German ISDN solutions and
a large number of international products are based on
Common ISDN API.
The international adoption of ISDN protocol specifica-
tions is now complete, and nearly all telecommunications
network operators provide BRI and PRI lines on the basis
of the international standard Q.931 / ETS 300 102.
Common ISDN API 2.0 is the CAPI version based on the
same standard. The experience gained over the past
years in the development of an ISDN applications
programming interface in Germany and other countries,
and the enormous base of installed CAPI solutions, have
contributed greatly to the development of this new
applications interface for international ISDN systems.
Over ten years of experience in the expanding ISDN
market have gone into CAPI 2.0. This version has all the
advantages of an open interface, and covers most ISDN
features (including data communications, telephony,
Group 3 fax and video conferencing). Since CAPI handles
the ISDN subscriber interface control functions, these no
longer have to be programmed. This simplifies the
development of ISDN applications. Furthermore,
applications no longer have to be tailored to national or
manufacturer-specific systems, so that a greater variety
of applications is available.
The use of Common ISDN API Version 2.0 supplies the
international market with comprehensive technology with
great profit potential.
CAPI 2.0
CAPI 1.1