IBM International ISDN, Руководство пользователя

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Appendix C: A Brief ISDN Glossary
ISDN PC Card – 17 Appendix C: A Brief ISDN Glossary 197
17 Appendix C: A Brief ISDN
Glossary
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This chapter gives a brief overview of technical terms used in
the world of ISDN as well as a few computer-related terms.
Historical Survey
The first steps in the development of ISDN –the Integrated
Services Digital Network– took place in the early 1980s in
France. Many other European countries soon joined in the
development work, however. ISDN was considered the logi-
cal successor to the analog telephony technology commonly
used in Europe at that time. ISDN offered the potential for
high speed bi-directional data communications at 64 kbit/s
or 128 kbit/s. The ISDN specifications were submitted to the
I TU and have since been standardized. However, I TU stan-
dards are only recommendations, and some countries have
implemented their own versions of ISDN. Thus ISDN proto-
cols are not exactly the same in every country. However, the
IBM International ISDN PC Card supports all major D-channel
switching protocols, so that this adapter can be used in a
great number of countries throughout the world.
Today ISDN is very easily implemented, since telephone
companies in most countries use only digital interfaces with-
in their networks. The difference between an analog tele-
phone line and an ISDN line today lies in the wire used from
the telephone company's exchange to the subscriber's ac-
cess interface, the type of signals traveling on these lines,
and the voltage. Hence you cannot connect an analog device
to an ISDN line, nor vice versa.