Integrated Services Digital Network

ISDN ISDNISDN30D-channelDigital Networkshigh speed connectionIntegrated Services Digital Network (ISDN)ISDN (data) phone linesISDN cardISDN2e
Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network.wikipedia
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Basic Rate Interface

BRIISDN BRI2B1D
The ISDN standards define several kinds of access interfaces, such as Basic Rate Interface (BRI), Primary Rate Interface (PRI), Narrowband ISDN (N-ISDN), and Broadband ISDN (B-ISDN).
Basic Rate Interface (BRI, 2B+D, 2B1D) or Basic Rate Access is an Integrated Services Digital Network (ISDN) configuration intended primarily for use in subscriber lines similar to those that have long been used for voice-grade telephone service.

Plain old telephone service

POTSLocal Telephone Servicetelephone
The key feature of ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system.
POTS was the standard service offering from telephone companies from 1876 until 1988 in the United States when the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) was introduced, followed by cellular telephone systems, and voice over IP (VoIP).

Primary Rate Interface

PRIprimary rateISDN30
The ISDN standards define several kinds of access interfaces, such as Basic Rate Interface (BRI), Primary Rate Interface (PRI), Narrowband ISDN (N-ISDN), and Broadband ISDN (B-ISDN).
The Primary Rate Interface (PRI) is a telecommunications interface standard used on an Integrated Services Digital Network (ISDN) for carrying multiple DS0 voice and data transmissions between the network and a user.

Q.931

Q.2931ITU-T Q.931Q931
In common use, ISDN is often limited to usage to Q.931 and related protocols, which are a set of signaling protocols establishing and breaking circuit-switched connections, and for advanced calling features for the user.
ITU-T Recommendation Q.931 is the ITU standard ISDN connection control signalling protocol, forming part of ''Digital Subscriber Signalling System No.

H.320

ISDN uses the H.320 standard for audio coding and video coding, including audio codecs such as G.711 (PCM) and G.728 (CELP), and discrete cosine transform (DCT) video codecs such as H.261 and H.263.
H.320 or Narrow-band visual telephone systems and terminal equipment is an umbrella Recommendation by the ITU-T for running Multimedia (Audio/Video/Data) over ISDN based networks.

H.261

ISDN uses the H.320 standard for audio coding and video coding, including audio codecs such as G.711 (PCM) and G.728 (CELP), and discrete cosine transform (DCT) video codecs such as H.261 and H.263.
H.261 was originally designed for transmission over ISDN lines on which data rates are multiples of 64 kbit/s.

Terminal adapter

ISDN terminal adapterterminal adaptors
However, these operators generally offered free hardware that also allows the use of POTS equipment, such as NTBAs with integrated terminal adapters.
In ISDN terminology, the terminal adapter connects a terminal (computer) to the ISDN network.

B channel

B-ChannelB' channelsbearer (B) channels
The 144 kbit/s overall payload rate is divided into two 64 kbit/s bearer channels ('B' channels) and one 16 kbit/s signaling channel ('D' channel or data channel).
B channel (bearer) is a telecommunications term which refers to the ISDN channel in which the primary data or voice communication is carried.

U interface

UU k0 U K0 -Interface
The U interface or U reference point is a Basic Rate Interface (BRI) in the local loop of an Integrated Services Digital Network (ISDN).

Circuit switching

circuit switchedcircuit-switchedcircuit-switched network
ISDN is a circuit-switched telephone network system, which also provides access to packet switched networks, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in potentially better voice quality than an analog phone can provide.
ISDN is one such service that uses a separate signalling channel while plain old telephone service (POTS) does not.

Network termination 1

NT1network termination type 1network terminator
Network Termination 1 (NT1) or Network Termination type 1 refers to equipment in an Integrated Services Digital Network (ISDN) that physically and electrically terminates the network at the customer's premises.

D channel

D' channeldata (D) channel
The 144 kbit/s overall payload rate is divided into two 64 kbit/s bearer channels ('B' channels) and one 16 kbit/s signaling channel ('D' channel or data channel).
D channel (delta channel) is a telecommunications term which refers to the ISDN channel in which the control and signalling information is carried.

H.263

H.263+H263H.263v2 Annex I
ISDN uses the H.320 standard for audio coding and video coding, including audio codecs such as G.711 (PCM) and G.728 (CELP), and discrete cosine transform (DCT) video codecs such as H.261 and H.263.
The H.263 standard was first designed to be utilized in H.324 based systems (PSTN and other circuit-switched network videoconferencing and videotelephony), but it also found use in H.323 (RTP/IP-based videoconferencing), H.320 (ISDN-based videoconferencing, where it was the most widely used video compression standard), RTSP (streaming media) and SIP (IP-based videoconferencing) solutions.

X.25

X.25 protocol suiteX25CCITT X.25 recommendation
X.25 can be carried over the B or D channels of a BRI line, and over the B channels of a PRI line.
An X.25 WAN consists of packet-switching exchange (PSE) nodes as the networking hardware, and leased lines, plain old telephone service connections, or ISDN connections as physical links.

Frame Relay

Frame-RelayframesLAPF
In theory, Frame Relay can operate over the D channel of BRIs and PRIs, but it is seldom, if ever, used.
Originally designed for transport across Integrated Services Digital Network (ISDN) infrastructure, it may be used today in the context of many other network interfaces.

ITU-T

CCITTITU Telecommunication Standardization SectorTelecommunication Standardization Sector
It was first defined in 1988 in the CCITT red book.

R interface

R interface or R reference point defines the point between a non-ISDN device and a terminal adapter (TA) which provides translation to and from such a device.

Business telephone system

PBXprivate branch exchangePABX
PRI-ISDN is popular throughout the world, especially for connecting private branch exchanges to the public switched telephone network (PSTN).
The modern key system now supports SIP, ISDN, analog handsets (in addition to its own proprietary handsets - usually digital) as well as a raft of features more traditionally found on larger PBX systems.

Fax

fax machinefacsimilefax machines
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.
Personal computers have also long been able to handle incoming and outgoing faxes using analog modems or ISDN, eliminating the need for a stand-alone fax machine.

Internet access

broadband internetbroadband Internet accessbroadband
In some countries, ISDN found major market application for Internet access, in which ISDN typically provides a maximum of 128 kbit/s bandwidth in both upstream and downstream directions.
Integrated Services Digital Network (ISDN) is a switched telephone service capable of transporting voice and digital data, and is one of the oldest Internet access methods.

Discrete cosine transform

DCTiDCTinverse discrete cosine transform
ISDN uses the H.320 standard for audio coding and video coding, including audio codecs such as G.711 (PCM) and G.728 (CELP), and discrete cosine transform (DCT) video codecs such as H.261 and H.263.

Videotelephony

videoconferencingvideo conferencingvideo chat
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. In a videoconference, ISDN provides simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group (room) videoconferencing systems.
Only in the late 20th century with the advent of powerful video codecs combined with high-speed Internet broadband and ISDN service did videotelephony become a practical technology for regular use.

Local loop

subscriber lineloopsubscriber loop
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.

Signalling System No. 7

SS7Signaling System 7Signalling System 7
Between telephone company switches, the signaling is performed via SS7.
The Telephone User Part (TUP) was adopted in Europe and the Integrated Services Digital Network (ISDN) User Part (ISUP) adapted for public switched telephone network (PSTN) calls was adopted in North America.