Appendix C: A Brief ISDN Glossary
ISDN PC Card – 17 Appendix C: A Brief ISDN Glossary
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AO/DI
Always On/Dynamic I SDN. This is an I SDN tech-
nology that was originally developed by IBM and
is now an open ISDN standard. This technology is
currently only used in the USA and Canada. AO/DI
allows the user to connect to an ISP (Internet Ser-
vice Provider) for example, then drop the idle B-
channel connection after a delay. A D-channel
connection is maintained, however, and permits
a quicker reconnection when data is queued.
B channel
One of the two channel types available in ISDN.
The B channel is primarily used for data transfer
at 64 kbit/s in each direction.
Basic-rate
interface (BRI)
Access to the ISDN network comes in two different
flavors, known as basic-rate and primary-rate ac-
cess. The basic-rate interface defines the use of
two B channels for bidirectional data transfer and
one D channel for signaling to control the commu-
nication over the B channels. The IBM Internation-
al ISDN PC Card is a BRI adapter.
BRI
See basic-rate interface.
CAPI
Common I SDN API . This is a programming inter-
face for ISDN that has been developed in Germa-
ny and is today a de facto standard for European
ISDN cards. CAPI allows software developers to
write ISDN-capable applications without having to
deal with specific ISDN adapter implementa-
tions– as long as the adapter is equipped with
CAPI drivers. Thus any CAPI-compliant application
software works out of the box on any CAPI-compli-
ant ISDN device. The CAPI interface is indepen-
dent both from the telephone company's imple-
mentation of ISDN and from the hardware manu-
facturer's implementation of the ISDN adapter.
CAPI is thus universal. The CAPI interface has
been defined for a broad range of operating sys-
tems, including DOS, Windows 3.x, Windows 95,
Windows NT, Linux, etc. More information can be
obtained from http://www.capi.org.
•
CAPI 1.1 was the original CAPI specification
for the German ISDN implementation.
Glossary
