ISDN
[2] By the time the standard was released, newer networking systems with much greater speeds were available, and ISDN saw relatively little uptake in the wider market.
At the time, the network was viewed as a way to transport voice, with some special services available for data using additional equipment like modems or by providing a T1 on the customer's location.
Although ISDN was successful in a few countries such as Germany, on a global scale the system was largely ignored and garnered the industry nickname "innovation subscribers didn't need.
"[4] It found a use for a time for small-office digital connection, using the voice lines for data at 64 kbit/s, sometimes "bonded" to 128 kbit/s, but the introduction of 56 kbit/s modems undercut its value in many roles.
Over the first half of the 20th century, the connection of these lines to form calls was increasingly automated, culminating in the crossbar switches that had largely replaced earlier concepts by the 1950s.
However, these connections now represented over 99% of the total telephony network, as the upstream links had increasingly been aggregated into a smaller number of much higher performance systems, especially after the introduction of fiber optic lines.
They studied a number of derivatives of the T1's AMI concept and concluded that a customer-side line could reliably carry about 160 kbit/s of data over a distance of 4 to 5 miles (6.4 to 8.0 km).
[4] A key problem was that the customer might only have a single twisted pair line to the location of the handset, so the solution used in T1 with separate upstream and downstream connections was not universally available.
A debate broke out between teams worldwide about the best solution to this problem; some promoted newer versions of echo cancellation, while others preferred the "ping pong" concept where the direction of data would rapidly switch the line from send to receive at such a high rate it would not be noticeable to the user.
The suggestion was literally laughed off the table (His boss told him to "sit down and shut up"[4]) but the echo cancellation concept that was taken up by Joe Lechleider eventually came to win the debate.
To further confuse issues, in 1984 the Bell System was broken up and the US center for development moved to the American National Standards Institute (ANSI) T1D1.3 committee.
Thomas Starr of the newly formed Ameritech led this effort and eventually convinced the ANSI group to select the 2B1Q standard proposed by Peter Adams of British Telecom.
With digital-quality voice made possible by ISDN, offering two separate lines and continuous data connectivity, there was an initial global expectation of high customer demand for such systems in both the home and office environments.
[5] Conversely, in Europe, ISDN found fertile ground for deployment, driven by regulatory support, infrastructural needs, and the absence of comparable high-speed communication technologies at the time.
The technology was widely embraced for its ability to digitalize the "last mile" of telecommunications, significantly enhancing the quality and efficiency of voice, data, and video transmission over traditional analog systems.
Another standards war broke out, but in 1991 Lechleider's 1.6 Mbit/s "High-Speed Digital Subscriber Line" eventually won this process as well, after Starr drove it through the ANSI T1E1.4 group.
Integrated services refers to ISDN's ability to deliver at minimum two simultaneous connections, in any combination of data, voice, video, and fax, over a single line.
Normally, a PBX is connected via a T1 with robbed bit signaling to indicate on-hook or off-hook conditions and MF and DTMF tones to encode the destination number.
Where very high quality audio is required multiple ISDN BRIs can be used in parallel to provide a higher bandwidth circuit switched connection.
In many countries, such as the UK and Australia, ISDN has displaced the older technology of equalised analogue landlines, with these circuits being phased out by telecommunications providers.
Use of IP-based streaming codecs such as Comrex ACCESS and ipDTL is becoming more widespread in the broadcast sector, using broadband internet to connect remote studios.
[20] A study[21] of the Germany's Federal Ministry of Education and Research shows the following share of ISDN-channels per 1,000 inhabitants in 2005: Telstra provides the business customer with the ISDN services.
Since then phone companies started introducing cheaper xDSL-only products using VoIP for telephony,[25] also in an effort to reduce their costs by operating separate data & voice networks.
Following the launch of ADSL in 2003, the importance of ISDN for data transfer began to decrease and is today limited to niche business applications with point-to-point requirements.
ISDN continues to be an important backup network for point-to-point leased line customers such as banks, e-Seva Centers,[27] Life Insurance Corporation of India, and SBI ATMs.
[28] Previously, in April 1985, Japanese digital telephone exchange hardware made by Fujitsu was used to experimentally deploy the world's first I interface ISDN.
In Japan, the number of ISDN subscribers dwindled as alternative technologies such as ADSL, cable Internet access, and fiber to the home gained greater popularity.
[37][38] Once the term "broadband" came to be associated with data rates incoming to the customer at 256 kbit/s or more, and alternatives like ADSL grew in popularity, the consumer market for BRI did not develop.
High-end videoconferencing hardware can bond up to 8 B-channels together (using a BRI circuit for every 2 channels) to provide digital, circuit-switched video connections to almost anywhere in the world.
This is very expensive, and is being replaced by IP-based conferencing, but where cost concern is less of an issue than predictable quality and where a QoS-enabled IP does not exist, BRI is the preferred choice.
