Integrated Services Digital Network or Isolated Subscriber Digital Network (ISDN), originally "Integriertes Sprach- und Datennetz" (German for "Integrated Speech and Data Net"), is a circuit-switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better voice quality than an analog phone. In Telecommunications a circuit switching network is one that establishes a fixed bandwidth circuit (or channel) between nodes and terminals Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics A digital system uses discrete (discontinuous values usually but not always Symbolized Numerically (hence called "digital" to represent information for In Telecommunications transmission is the process of sending propagating and receiving an analogue or digital information signal over a physical point-to-point or Debt AIDS Trade in Africa (or DATA) is a Multinational non-government organization founded in January 2002 in London by U2 's The public switched telephone network ( PSTN) is the network of the world's public circuit-switched Telephone networks in much the same way that the It offers circuit-switched connections (for either voice or data) in increments of 64 kbit/s. Another major use case is Internet access, where ISDN typically provides a maximum of 128 kbit/s (which can be considered to be broadband speed, since it exceeds the narrowband speeds of 56k telephone lines). The Internet is a global system of interconnected Computer networks The term broadband can have different meanings in different contexts More broadly, ISDN is a set of protocols for establishing and breaking circuit switched connections, and for advanced call features for the user. In computing, a protocol is a convention or standard that controls or enables the connection Communication, and Data transfer between two computing In Telecommunication, signalling (UK spelling or signaling (US spelling has the following meanings The use of signals for controlling communications It was introduced in the late 1980s. 
In a videoconference, ISDN provides simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group (room) videoconferencing systems. A videoconference (also known as a videoteleconference) is a set of interactive Telecommunication technologies which allow two or more locations to interact
The purpose of the ISDN is to provide fully integrated digital services to the users. These services fall under three categories: bearer services, supplementary services and teleservices.
The entry level interface to ISDN is the Basic Rate Interface (BRI) is a 144 kbit/s service delivered over a pair of standard telephone copper wires. In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission The 144 kbit/s rate is broken down into two 64 kbit/s data channels ('B' channels) and one 16 kbit/s signalling channel ('D' channel).
The Interface specifies three different network interfaces:
The other ISDN service available is the Primary Rate Interface (PRI) which is an E1 (2048 kbit/s) in most parts of the world. An E1 is 30 'B' channels of 64 kbit/s, one 'D' channel of 64 kbit/s and a timing and alarm channel of 64 kbit/s. North America and Japan use T1s of 1544 kbit/s. A T1 has 23 'B' channels and 1 'D' channel for signalling.
The data channel (B) is a standard 64 kbit/s voice channel of 8 bits sampled at 8 kHz and uses G. 711. Alternately it can be a 64 kbit/s data stream between digital devices.
The signalling channel (D) uses Q.931 for signalling with the other side of the link. ITU-T Recommendation Q931 is ISDN 's connection control protocol, roughly (not at the same layer comparable to TCP in the Internet
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. Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information The typical end-user's connection to the Internet is related to this point of view, and discussion on the merits of various ISDN modems, carriers' offerings and tarriffing (features, pricing) are from this perspective. The Internet is a global system of interconnected Computer networks 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.
There is a second viewpoint: that of the telephone industry, where ISDN is a core technology. 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. In digital Telecommunications where a single physical wire pair can be used to carry many simultaneous voice conversations worldwide standards have been created and deployed On a normal T1, the signalling is done with A&B bits to indicate on-hook or off-hook conditions and MF and DTMF tones to encode the destination number. In Telephony Multi-Frequency (MF is an outdated in-band signaling technique Dual-tone multi-frequency ( DTMF) signaling is used for Telephone signaling over the line in the voice-frequency band to the call switching center ISDN is much better because messages can be sent much more quickly than by trying to encode numbers as long (100 ms per digit) tone sequences. ENCODE (the ENC yclopedia O f D NA E lements is a public research consortium launched by the US National Human Genome Research Institute ( NHGRI 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.
It is also used as a smart-network technology intended to add new services to the public switched telephone network (PSTN) by giving users direct access to end-to-end circuit-switched digital services. The public switched telephone network ( PSTN) is the network of the world's public circuit-switched Telephone networks in much the same way that the
ISDN BRI (Basic Rate Interface) has never gained popularity as a telephone access technology in the United States and today remains a niche product. Basic rate interface (BRI 2B+D 2B1D is an Integrated Services Digital Network (ISDN configuration defined in the physical layer standard I The service was seen as a solution in search of a problem, and the extensive array of options and features were difficult for most customers to understand and utilize. ISDN has long been known by several
derogatory acronyms highlighting these issues, such as It Still Does Nothing, Innovations Subscribers Don't Need, and I Still Don't kNow.
Part of the difficulty is that as ISDN was coming into service, the concept of what the word broadband meant was being revised upward to mean at least 256 kbit/s incoming to the customer. The term broadband can have different meanings in different contexts As ADSL grew in popularity in the United States, the consumer market for ISDN imploded. Asymmetric Digital Subscriber Line ( ADSL) is a form of DSL, a data communications technology that enables faster data transmission over Copper Telephone Its only remaining positive element is that while ADSL has a functional distance limitation, ISDN does not have any such limit and may be acceptable in situations where the customer is too remote for ADSL to work. This is further stymied by many North American CLECs having given up on ISDN and will not install it as a new option for remote/rural exchanges.
However, most modern non-VoIP PBXs use PRI (Primary Rate Interface) T1 lines to communicate with a Telco Class 5 central office switch, replacing older analog two-way and Direct Inward Dialing (DID) trunks. The primary rate interface (PRI is a Telecommunications standard for carrying multiple DS0 voice and data transmissions between two physical locations In Telecommunications T-carrier, sometimes abbreviated as T-CXR, is the generic designator for any of several digitally multiplexed telecommunications Direct Inward Dialing (DID, also called Direct Dial-In (DDI in Europe is a feature offered by telephone companies for use with their customers' PBX systems PRI is capable of delivering Automatic Number Identification (ANI) in both directions so that the telephone number of an extension, rather than a company's main number, can be sent. Automatic Number Identification (ANI is a feature of Telephony Intelligent network services that permits subscribers to display or capture the Telephone 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. A recording studio is a facility for sound recording. Ideally the space is specially designed by an acoustician to achieve the desired acoustic properties (sound ISDN is used because of its "guaranteed" real-time, not-over-the-Internet service, and its superior audio fidelity as compared to POTS service. A few companies make video conference call equipment that combine three BRI lines (containing six 64K channels) to create a good quality picture.
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. Asymmetric Digital Subscriber Line ( ADSL) is a form of DSL, a data communications technology that enables faster data transmission over Copper Telephone NTT, a dominant Japanese telephone company, provides an ISDN service with the names INS64 and INS1500, which are much less recognized than ISDN. commonly known as NTT, is a telephone company that dominates the Telecommunication market in Japan. A telephone company (or telco) provides Telecommunications services such as Telephony and Data communications Most of the largest telcos whatever
In the UK, British Telecom (BT) provides ISDN2e (BRI) as well as ISDN30 (PRI). The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located BT Group plc (formerly British Telecommunications plc) which trades as BT (ˌbiːˈtiː bee tee) (previously known as British Telecom and still Basic rate interface (BRI 2B+D 2B1D is an Integrated Services Digital Network (ISDN configuration defined in the physical layer standard I The primary rate interface (PRI is a Telecommunications standard for carrying multiple DS0 voice and data transmissions between two physical locations Until April 2006, they also offered Home Highway and Business Highway, which are BRI ISDN-based services that offer integrated analogue connectivity as well as ISDN. Later versions of the Highway products also included built-in USB sockets for direct computer access. Home Highway has been bought by many home users, usually for Internet connection, although not as fast as ADSL, because it was available before ADSL and in places where ADSL does not reach. Virgin Media also use ISDN lines for customer of Virgin Broadband who live in cable tv areas. Virgin Media Inc (formerly known as ntlTelewest, after a merger of NTL Incorporated with Telewest Global Inc Virgin Broadband may refer to Virgin Broadband (Australia Virgin Media (UK
France Télécom offers ISDN services under their product name Numeris (2 B+D), of which a professional Duo and home Itoo version is available. France Télécom () is the main Telecommunication company in France and one of the largest in the world 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, and for applications such as business voice and point-of-sale terminals. A private branch exchange (PBX is a Telephone exchange that serves a particular business or office as opposed to one that a Common carrier or telephone company Point of sale or point of service ( POS or PoS) can mean a retail shop, a checkout counter in a shop or the location where a transaction
In Germany, ISDN is very popular with an installed base of 25 million channels (29% of all subscriber lines in Germany as of 2003 and 20% of all ISDN channels worldwide). Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. Due to the success of ISDN, the number of installed analog lines is decreasing. Deutsche Telekom (DTAG) offers both BRI and PRI. Deutsche Telekom AG (,) ( English translation German Telecom) (abbreviated DTAG) is a Telecommunications company headquartered in Competing phone companies often offer ISDN only and no analog lines. Because of the widespread availability of ADSL services, ISDN is today primarily used for voice and fax traffic, but is still very popular thanks to the pricing policy of German telecommunication providers. Today ISDN (BRI) and ADSL/VDSL are often bundled on the same line. , mainly because the combination of ADSL with an analog line has no cost advantage over a combined ISDN-ADSL line.
In India, ISDN was very popular until the introduction of ADSL. India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country Asymmetric Digital Subscriber Line ( ADSL) is a form of DSL, a data communications technology that enables faster data transmission over Copper Telephone Bharat Sanchar Nigam Limited, the largest communication service provider in India and a state owned company, is offering both ISDN BRI and PRI services across the country over its ISDN network. Bharat Sanchar Nigam Limited (known as BSNL, India Communications Corporation Limited) is a Public sector communications company After the introduction of ADSL broadband technology with static IPs, the data transfer load is taken up by ADSL. But ISDN still plays a very big role as a backup network for point-to-point leased line customers and low cost reliable data network for organisations located all over India, such as banks, E-seva centres, Life Insurance Corporation of India, and so on. The Life Insurance Corporation of India (LIC is the largest Life insurance company in India and also the country's largest investor
A study  of the German Department of Science shows the following spread of ISDN-channels per 1000 inhabitants in the year 2005:
In ISDN, there are two types of channels, B (for "Bearer") and D (for "Delta"). B channels are used for data (which may include voice), and D channels are intended for signaling and control (but can also be used for data).
There are two ISDN implementations. Basic Rate Interface (BRI), also called Basic Rate Access (BRA) in Europe — consists of two B channels, each with bandwidth of 64 kbit/s, and one D channel with a bandwidth of 16 kbit/s. Basic rate interface (BRI 2B+D 2B1D is an Integrated Services Digital Network (ISDN configuration defined in the physical layer standard I In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission Together these three channels can be designated as 2B+D. Primary Rate Interface (PRI), also called Primary Rate Access (PRA) in Europe — contains a greater number of B channels and a D channel with a bandwidth of 64 kbit/s. The primary rate interface (PRI is a Telecommunications standard for carrying multiple DS0 voice and data transmissions between two physical locations The number of B channels for PRI varies according to the nation: in North America and Japan it is 23B+1D, with an aggregate bit rate of 1. 544 Mbit/s (T1); in Europe, India and Australia it is 30B+1D, with an aggregate bit rate of 2. In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission 048 Mbit/s (E1). In digital Telecommunications where a single physical wire pair can be used to carry many simultaneous voice conversations worldwide standards have been created and deployed Broadband Integrated Services Digital Network (BISDN) is another ISDN implementation and it is able to manage different types of services at the same time. In the 1980s the Telecommunications industry expected that digital services would follow much the same pattern as voice services did on the Public switched telephone network, In the 1980s the Telecommunications industry expected that digital services would follow much the same pattern as voice services did on the Public switched telephone network, It is primarily used within network backbones and employs ATM. A backbone network or network backbone is a part of Computer network infrastructure that interconnects various pieces of network providing a path for the exchange In electronic digital data transmission systems the Network protocol Asynchronous Transfer Mode (ATM encodes data traffic into small fixed-sized cells
Another alternative ISDN configuration can be used in which the B channels of an ISDN basic rate interface are bonded to provide a total duplex bandwidth of 128 kbit/s. Basic rate interface (BRI 2B+D 2B1D is an Integrated Services Digital Network (ISDN configuration defined in the physical layer standard I This precludes use of the line for voice calls while the internet connection is in use.
Using bipolar with eight-zero substitution encoding technique, call data is transmitted over the data (B) channels, with the signalling (D) channels used for call setup and management. B8ZS is an abbreviation for Bipolar with 8 Zeros Substitution (not Binary Eight Zero Substitution see discussion- which is a method of line coding used in the T-carrier Once a call is set up, there is a simple 64 kbit/s synchronous bidirectional data channel between the end parties, lasting until the call is terminated. There can be as many calls as there are bearer channels, to the same or different end-points. Bearer channels may also be multiplexed into what may be considered single, higher-bandwidth channels via a process called B channel bonding. For multiplexing in electronics and signal processing see Multiplexer.
The D channel can also be used for sending and receiving X.25 data packets, and connection to X. X25 is an ITU-T standard Network layer protocol for packet switched Wide area network (WAN communication 25 packet network, this is specified in X. 31. In practice, X. 31 was only commercially implemented in UK, France and Japan.
A set of reference points are defined in the ISDN standard to refer to certain points between the telco and the end user ISDN equipment. Reference Point is the first album by Acoustic Alchemy for jazz label GRP and their fourth album overall International standards are Standards developed by international Standards organisations International standards are available for consideration and use worldwide A telephone company (or telco) provides Telecommunications services such as Telephony and Data communications Most of the largest telcos whatever
1 Most NT-1 devices can perform the functions of the NT-2 as well, and so the S and T reference points are generally collapsed into the S/T reference point. R interface defines the point between a non- ISDN device and a terminal adapter (TA which provides translation to and from such a device ISDN In ISDN terminology a terminal adapter or TA is a device that connects a terminal (computer to the ISDN network S interface: For basic rate Access in an Integrated Services Digital Network (ISDN environment a User-Network Interface Reference point that A T-interface is used for Basic rate access in an Integrated Services Digital Network (ISDN environment Network Termination 1 (NT1 In Integrated Services Digital Networks ( ISDN) a functional grouping of customer-premises equipment that includes functions
² Inside North America, the NT-1 device is considered customer premises equipment(CPE) and must be maintained by the customer, thus, the U interface is provided to the customer. Customer-premises equipment or customer-provided equipment ( CPE) is any terminal and associated Equipment located at a Subscriber In other locations, the NT-1 device is maintained by the telco, and the S/T interface is provided to the customer. In India, service providers provide U interface and an NT1 may be supplied by Service provider as part of service offering
Among the kinds of data that can be moved over the 64 kbit/s channels are pulse-code modulated voice calls, providing access to the traditional voice PSTN. The public switched telephone network ( PSTN) is the network of the world's public circuit-switched Telephone networks in much the same way that the This information can be passed between the network and the user end-point at call set-up time. In North America, ISDN is now used mostly as an alternative to analog connections, most commonly for Internet access. Some of the services envisioned as being delivered over ISDN are now delivered over the Internet instead. In Europe, and in Germany in particular, ISDN has been successfully marketed as a phone with features, as opposed to a POTS phone (Plain Old Telephone Service) with few or no features. Meanwhile, features that were first available with ISDN (such as Three-Way Call, Call Forwarding, Caller ID, etc. ) are now commonly available for ordinary analog phones as well, eliminating this advantage of ISDN. Another advantage of ISDN was the possibility of multiple simultaneous calls (one call per B channel), e. g. for big families, but with the increased popularity and reduced prices of mobile telephony this has become less interesting as well, making ISDN unappealing to the private customer. However, ISDN is typically more reliable than POTS, and has a significantly faster call setup time compared with POTS, and IP connections over ISDN typically have some 30–35ms round trip time, as opposed to 120–180ms (both measured with otherwise unused lines) over 56k or V. 34 modems, making ISDN more pleasant for telecommuters.
Where an analog connection requires a modem, an ISDN connection requires a terminal adapter (TA). Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information ISDN In ISDN terminology a terminal adapter or TA is a device that connects a terminal (computer to the ISDN network The function of an ISDN terminal adapter is often delivered in the form of a PC card with an S/T interface, and single-chip solutions seem to exist, considering the plethora of combined ISDN- and ADSL-routers. Asymmetric Digital Subscriber Line ( ADSL) is a form of DSL, a data communications technology that enables faster data transmission over Copper Telephone A router ('rautər in the USA 'rutər in the UK and Ireland, or either pronunciation in Australia and Canada is a Computer whose software and hardware are usually
ISDN is commonly used in radio broadcasting. This article is about radio broadcasting for other uses see Radio (disambiguation. Since ISDN provides a high quality connection this assists in delivering good quality audio for transmission in radio. Most radio studios are equipped with ISDN lines as their main form of communication with other studios or standard phone lines.
The following is an example of a Primary Rate (PRI) ISDN call showing the Q. 921/LAPD and the Q.931/Network message intermixed (i. Link Access Procedures on the D channel (LAPD, specified in ITU-T Q ITU-T Recommendation Q931 is ISDN 's connection control protocol, roughly (not at the same layer comparable to TCP in the Internet e. exactly what was exchanged on the D-channel). The call is originating from the switch where the trace was taken and goes out to some other switch, possibly an end-office LEC, who terminates the call. Local Exchange Carrier (LEC is a Regulatory term in Telecommunications for the local telephone company
The first line format is <time> <D-channel> <Transmitted/Received> <LAPD/ISDN message ID>. If the message is an ISDN level message, then a decoding of the message is attempted showing the various Information Elements that make up the message. All ISDN messages are tagged with an ID number relative to the switch that started the call (local/remote). Following this optional decoding is a dump of the bytes of the message in <offset> <hex> . . . <hex> <ascii> . . . <ascii> format.
The RR messages at the beginning prior to the call are the keep alive messages. Then you will see a SETUP message that starts the call. Each message is acknowledged by the other side with a RR.
10:49:47. 33 21/1/24 R RR0000 02 01 01 a5 . . . . 10:49:47. 34 21/1/24 T RR0000 02 01 01 b9 . . . . 10:50:17. 57 21/1/24 R RR0000 02 01 01 a5 . . . . 10:50:17. 58 21/1/24 T RR0000 02 01 01 b9 . . . . 10:50:24. 37 21/1/24 T SETUP Call Reference : 000062-local Bearer Capability : CCITT, Speech, Circuit mode, 64 kbit/s Channel ID : Implicit Interface ID implies current span, 21/1/5, Exclusive Calling Party Number : 8018023000 National number User-provided, not screened Presentation allowed Called Party Number : 3739120 Type: SUBSCRB0000 00 01 a4 b8 08 02 00 3e 05 04 03 80 90 a2 18 03 . . . . . . . >. . . . . . . . 0010 a9 83 85 6c 0c 21 80 38 30 31 38 30 32 33 30 30 . . . l. !. 8018023000020 30 70 08 c1 33 37 33 39 31 32 30 0p. . 373912010:50:24. 37 21/1/24 R RR0000 00 01 01 a6 . . . . 10:50:24. 77 21/1/24 R CALL PROCEEDING Call Reference : 000062-local Channel ID : Implicit Interface ID implies current span, 21/1/5, Exclusive0000 02 01 b8 a6 08 02 80 3e 02 18 03 a9 83 85 . . . . . . . >. . . . . . 10:50:24. 77 21/1/24 T RR0000 02 01 01 ba . . . . 10:50:25. 02 21/1/24 R ALERTING Call Reference : 000062-local Progress Indicator : CCITT, Public network serving local user, In-band information or an appropriate pattern is now available0000 02 01 ba a6 08 02 80 3e 01 1e 02 82 88 . . . . . . . >. . . . . 10:50:25. 02 21/1/24 T RR0000 02 01 01 bc . . . . 10:50:28. 43 21/1/24 R CONNECT Call Reference : 000062-local0000 02 01 bc a6 08 02 80 3e 07 . . . . . . . >. 10:50:28. 43 21/1/24 T RR0000 02 01 01 be . . . . 10:50:28. 43 21/1/24 T CONNECT_ACK Call Reference : 000062-local0000 00 01 a6 be 08 02 00 3e 0f . . . . . . . >. 10:50:28. 44 21/1/24 R RR0000 00 01 01 a8 . . . . 10:50:35. 69 21/1/24 T DISCONNECT Call Reference : 000062-local Cause : 16, Normal call clearing. 0000 00 01 a8 be 08 02 00 3e 45 08 02 8a 90 . . . . . . . >E. . . . 10:50:35. 70 21/1/24 R RR0000 00 01 01 aa . . . . 10:50:36. 98 21/1/24 R RELEASE Call Reference : 000062-local0000 02 01 be aa 08 02 80 3e 4d . . . . . . . >M10:50:36. 98 21/1/24 T RR0000 02 01 01 c0 . . . . 10:50:36. 99 21/1/24 T RELEASE COMPLETE Call Reference : 000062-local0000 00 01 aa c0 08 02 00 3e 5a . . . . . . . >Z10:50:36. 00 21/1/24 R RR0000 00 01 01 ac . . . . 10:51:06. 10 21/1/24 R RR0000 02 01 01 ad . . . . 10:51:06. 10 21/1/24 T RR0000 02 01 01 c1 . . . . 10:51:36. 37 21/1/24 R RR0000 02 01 01 ad . . . . 10:51:36. 37 21/1/24 T RR0000 02 01 01 c1 . . . .
Specifications defining the physical layer and part of the data link layers of ISDN:
From the point of view of the OSI architecture, an ISDN line has a stack of three protocols
Asymmetric Digital Subscriber Line ( ADSL) is a form of DSL, a data communications technology that enables faster data transmission over Copper Telephone In electronic digital data transmission systems the Network protocol Asynchronous Transfer Mode (ATM encodes data traffic into small fixed-sized cells In the 1980s the Telecommunications industry expected that digital services would follow much the same pattern as voice services did on the Public switched telephone network, The Internet is a global system of interconnected Computer networks H320 is an umbrella recommendation by the ITU-T for running Multimedia (Audio/Video/Data over ISDN based networks The European Telecommunications Standards Institute ( ETSI) is an independent non-for-profit Standardization organization of the Telecommunications This is a list of device bandwidths: the Net bit rate (or more informally Digital bandwidth) of some computer devices employing methods of data transport is quantified