Integrated Services Digital Network

:ISDN is also short for isosorbide dinitrate

Consumer and industry perspectives

There are two points of view into the ISDN world. The most common viewpoint is that of the end user who wants to get a digital connection into the telephone/data network from home, whose performance would be better than an ordinary analog modem connection. The typical end-user's connection to the Internet is related to this point of view, and talk about the merits of various ISDN modems, carriers' offerings and tarriffing (features, pricing) are from this perspective. Much of the following discussion is from this point of view, but it should be noted that as a data connection service, ISDN has been mostly superseded by DSL. Because most incumbent telcos were deeply

Related Topics:
Modem - DSL

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reluctant to roll out end-user digital service at reasonable prices until the

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cable modem prodded many of them to provide DSL, within the computer networking

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community ISDN is often given the sardonic translation "It Still Does Nothing."

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There is however a second viewpoint: that of the telephone industry, where ISDN is not a dead issue. A telephone network can be thought of as a collection of wires strung between switching systems. The common electrical specification for the signals on these wires is T1 or E1. On a normal T1, the signalling is done with A&B bits to indicate on or off hook conditions and MF and DTMF tones to encode the destination number. ISDN is much better than this as messages can be sent much more quickly than by trying to encode numbers as long (100 ms per digit) tone sequences. This translated to much faster call setup times which is greatly desired by carriers who have to pay for line time and also by callers who become impatient while their call hops from switch to switch.

Related Topics:
T1 - E1 - MF - DTMF

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It is also used as a smart network technology intended to add new services to the public switched telephone network (the PSTN) by giving users direct access to end-to-end circuit-switched digital services.

Related Topics:
Smart network - Public switched telephone network - PSTN

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ISDN has never gained popularity as a telephone network in the United States and today remains a niche product. It is still commonly used in recording studios, when a voice-over actor is in one studio, but the director and producer are in a studio at another location. ISDN is used because of its "guaranteed" real-time, not-over-the-Internet service, and its superior audio fidelity as compared to POTS service.

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In Japan, it became popular to some extent from around 1999 to 2001, but now that ADSL has been introduced, the number of subscribers is in decline. NTT, a dominant Japanese telephone company, provides an ISDN service with the names INS64 and INS1500, which are much less recognized than ISDN.

Related Topics:
Japan - 1999 - 2001 - ADSL - NTT - Telephone company

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In the UK, British Telecom (BT) provides Home Highway and Business Highway, which are BRI ISDN services which offer connection from analog devices (such as normal phones) as well as ISDN devices (such as PCs equipped with terminal adapters). Home Highway has been bought by many home users, usually for Internet connection. Although not as fast as ADSL, it was available before ADSL, and in places where ADSL does not reach. BT also offers PRI ISDN.

Related Topics:
UK - British Telecom - Home Highway - Business Highway - PC - Terminal adapter - Internet - ADSL

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In France, France Télécom offers ISDN services under their product name Numeris (2 B+D) of which a profesional Duo and home Itoo version is available. ISDN is generally known as RNIS in France and has widespread availability. The introduction of ADSL is reducing ISDN use for data transfer and internet access, although it is still common in more rural and outlying areas.

Related Topics:
France - France Télécom - Numeris - Duo - Itoo - RNIS

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In Germany, ISDN is very popular with an installed base of 25 mio. channels (29% of all subscriber lines in Germany as of 2003 and 20% of all ISDN channels worldwide). Due to the success of ISDN, the number of installed analog lines is decreasing. Deutsche Telekom (DTAG) offers both BRI and PRI. Competing phone companies often offer ISDN only and no analog lines.

Related Topics:
Germany - 2003 - Deutsche Telekom

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