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ADSL
Asymmetric digital subscriber line. A form of digital communications
that can support up to 6 Mbps for downloading.
Analog
Communications
Method of voice transmission used in telephone systems. This
method converts voice to electrical signals and amplifies them
so that the voice can be sent over great distances. Analog transmission
has been the standard way of communicating via modem. It is, however,
the least effective at providing telecommunications bandwidth.
Asynchronous
Communication
The form of data communications that transmits data one character
at a time with start and stop bits. This is the method used over
POTS with modems.
ATM
Asynchronous Transfer Mode. A form of fast packet switching
that allows for data transmission via Broadband ISDN, a faster
form of digital communications that ISDN.
AT&TŪ
"5ESS"
The name of central office equipment manufactured by AT&T.
It is the leading telephone switch platform. These switches use
Custom (proprietary) or NI-I software.
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B -
B-Channel
A 64 kilobit-per-second bearer channel. The standard BRI connection
includes 2 B channels, for an uncompressed capacity of 28Kbps.
Bandwidth
The amount of data that be forced through a given channel.
The greater the bandwidth, the more data that can travel at one
time.
Bandwidth
Allocation Control Protocol (BACP)
The set of rules that manage bandwidth over PPP dynamic multilink
connections.
Basic
Rate Interface (BRI)
The standard ISDN line, consisting of 2 B-channels and 1 D-channel.
Bearer
Services
A communication connection's capability to carry voice, circuit,
or packet data. The 2 B channels in a BRI connection are bearer
channels.
Bellcore
Bell Communications Research. The research arm of the RBOCs.
Bellcore was part of Bell Laboratories before the breakup of AT&T.
Bellcore plays a leading role in developing ISDN standards and
other ISDN activities among its member telephone companies
Bonding
Bandwidth On Demand Interoperability Group. The merging of
two or more B channels to form a single channel with a bandwidth
greater than 64Kbps.
bps
Bits per second. The unit of measurement for data transmission
speed over a data communications line
BRI
Basic Rate Interface. A defined interface to ISDN that includes
two B channels and one Data channel. Commonly referred to 2b+d.
Bridge
A device that connects two or more networks and forwards information
between them. A bridge is sometimes called a data link relay or
a level 2 relay. A bridge is typically simpler and less expensive
than a router, but can only carry limited information from one
network to another.
BISDN
Broadband ISDN. A type of ISDN services that uses fiber-optic
lines and ATM to deliver bearer services with data transmission
rates of more than 150 Mbps. This is the next generation of ISDN
service that will replace ISDN delivered via the copper wiring
used today.
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C -
CACH
EKTS
Call Appearance Call Handling Electronic Key Telephone Service.
Supplements EKTS to allow more than one directory number and multiple
call appearances on each directory number.
Call
Appearances
A supplementary ISDN service that allows multiple incoming
calls. Each directory number can have multiple call appearances,
depending on the switch type.
CAPI
Common ISDN API. A collection of functions for handling ISDN
communications at the messaging level.
Central
Office (CO)
The telephone company's local facility that provides telephone
service in your area.
CENTREX
A service provided by a central office that provides a virtual
PBX to a set of extensions. It offers features such as transfer,
conference, and forward within that set of extensions.
Circuit
Switching
A form of communications in which an information transmission
path between two devices is routed through one or more switches.
The path is assigned for the duration of a call.
Cloud
A commonly used term that refers to any large network.
CO
Central office. The site where the local telephone switches
reside for all the telephone system's call routing and other functions.
This is the telephone company side of the local loop.
CODEC
coder/decoder. Transfers analog data into a digital data form
and converts digital data back to analog form.
Common
Carrier
Telephone companies that provide long-distance telecommunication
services, such as AT&T and MCI.
Compression
A process for reducing the number of bits required to transmit
information. Data transmission speeds up as much as 4 times faster
when compression is applied to an ISDN connection.
CPE
Customer Premises Equipment. The equipment after
the point at which the telephone company terminates the line to
the premises. End users must purchase or lease, install, and maintain
their own CPE.
CSD
Circuit-Switched Data. An ISDN circuit-switched call for data
in which a transmission path between two users is assigned for
the duration of a call at a constant, fixed rate.
Customer
Access Line Charge (CALC)
A federal tariff for hooking up your ISDN line. Also referred
to as an End User Common Line Charge (EUCL), or Subscriber Line
Charge (SLC). Every ISDN line is charged one CALC or EUCL. The
amount varies by state or province.
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D -
Demarc
The "demarcation point", or the point where the
telephone company's wiring stops and your wiring begins. In other
words, the phone company will charge you extra for any wiring
work performed on your side of the demarc. The physical device
that connects the phone company's wire to the premises wiring
is called a network interface box.
D-Channel
One of the three standard channels on a Basic Rate ISDN line.
At 16 kilobits per second, a D-channel can carry signaling information
and low-speed packet data.
DMS-100
The name of central office equipment manufactured by Northern
Telecom.
DN
Directory number. Each BRI connection can have up to two directory
numbers, one for each B channel. Directory numbers are telephone
numbers for ISDN.
DSSI
Digital Subscriber Signaling System No. 1. The network access
signaling protocol for users connecting to ISDN. It includes the
CCITT Q.931 and Q.932 standards.
DTE
Data Terminal Equipment. Any device that converts information
into digital signals for transmission or reconverts digital information
into another form.
Dynamic
Bandwidth Allocation
A feature of ISDN remote-access devices that allows
automatic adjustment of the numbers of B channels in use depending
on the volume being sent and received.
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EKTS
Electronic Key Telephone Service. The National ISDN-1 standard
for working with supplementary service on an ISDN telephone or
analog telephone connected to an NT1 Plus device.
Ethernet
The local area network protocol used in most PC networks.
Typically, most Ethernet networks support data transmission speeds
up to 10 Mbps.
EWSD
The name of central office equipment manufactured by Siemens
Stromberg-Carlson.
Exchange
See central office.
Exchange
Area
A geographical area in which a single, uniform set of tariffs
for telephone service is in place. A call between any a two points
in an exchange area is considered a local call.
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F -
FCC
Federal Communications Commission The US government agency
responsible for regulating the telephone industry.
Fiber
Optics
A new generation of telecommunications wiring that uses light
beams sent through thin strands of glass.
Full
Duplex
The bi-directional communication capability in which transmissions
can travel in both directions simultaneously.
Functional
Devices
A classification of ISDN operational functions used to describe
what tasks different components of an ISDN configuration perform.
For example, the Network Termination 1 function defines the NT1
device that presents your premises as a node on the ISDN network.
Another functional device is the terminal adapter, which defines
the role of an adapter to convert some other form of communication
to ISDN. For example, a TA allows an analog telephone to communicate
over an ISDN device.
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Group
3 Fax
Currently, the most widely used facsimile protocol, which
operates over analog telephone lines or with a terminal adapter
over ISDN.
Group
4 Fax
A facsimile protocol that allows high-speed, digital fax machines
to operate over ISDN.
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Half
Duplex
Data transmission that only takes place one direction at a
time.
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IEC
InterExchange Carrier. The telephone company that provides
telephone service outside the local telephone companies. For example,
AT&T and MCI are InterExchange Carriers. InterExchange Carriers
are also referred to as common carriers.
IEEE
803.2
The protocol that defines an Ethernet network at the physical
layer of network signaling and cabling.
In-band
signaling
Network signaling that is carried in the same channel as the
bearer traffic. In analog telephone communication, the same circuits
used to carry voice are used to transmit the signal for the telephone
network. Touch Tone signals are an example of in-band signaling.
Inside
Wiring
Wiring work that, in order for you to have an ISDN line, may
need to be done on your side of the demarc. Typically, you have
the option of doing it yourself or having the phone company do
it for an extra charge.
Interface
A specification that defines the protocols used at a particular
reference point in a network. The Basic Rate Interface (BRI) refers
to an access interface to ISDN.
Interoperable
Two pieces of equipment are interoperable when they work together.
Standards make device from different vendors work with each other.
For example, the H.320 standard for video conferencing allowing
you to use an Intel ProShare system to connect to a Vivo320 system.
ISDN
Integrated Services Digital Network: A completely digital
telephone/telecommunications network for carrying voice, data,
images, and video at high speed by sending digitally-encoded signals.
ISDN provides "end-to-end" digital service and can work
on the copper wiring phone lines that are in most homes and businesses
today.
ISDN
address
The address of a specific ISDN device. It comprises an ISDN number
plus additional digits that identify a specific terminal at a
user's interface. An ISDN number is the network address associated
with a user's ISDN connection.
ISDN
Ordering Code
A predefined number that tells the phone company how to provision
your ISDN line based on the requirements of your ISDN hardware.
ISDN
telephone
A telephone designed for ISDN service. It typically includes programmable
buttons for managing call features and an LCD display for viewing
caller information.
ITC
Independent Telephone Company. In the U.S., a telephone company
that was not owned by AT&T prior to divestiture.
ITU
International Telecommunications Union. An organization under
the United Nations that prepares telecommunication recommendations
or standards, including many related to ISDN. The ITU was formally
the CCITT.
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K -
Kbps
Kilobits per second. The unit of measurement in thousands
of bits per second for data transmission.
Key
systems
Telephone equipment with extra buttons that provides users
with more functionality than regular telephones. ISDN phones and
NT1 Plus devices that support analog telephone include key systems.
A key system in a protocol invoked when you press a sequence of
keys on the analog or ISDN telephone's dialing pad.
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L -
LAN
Local area network. A group of computer and other devices
linked via a network operating system. LANs vary in size but are
restricted to a single location because of cabling limitations.
The leading protocol for LANs is Ethernet. Leading PC LANS include
Novell's NetWare, Windows for Workgroups, and Windows NT.
LATA
Local Area Transport Area. Local exchange carriers (RBOCs)
provide service within a LATA. Typically a LATA comprises multiple
area codes. In most cases RBOCs are prohibited from offering telecommunication
services between LATAs.
LEC
Local Exchange Carrier. The local telephone company. An LEC
is also called an RBOC (Regional Bell Operating Company).Line
Extension
A
means for providing ISDN at distances beyond the normal limit
between the central office and your location
Local
Loop
The pair of copper wires that connects the end user to the
telephone company's central office. These wires, originally installed
for analog communications, are the same wires used for ISDN service
but require new equipment at the end user's premises and at the
telephone company.
Loop
or Line Qualification
A test that your phone company runs to make sure that your
ISDN line meets the distance and quality requirements of 18,000
feet from the central office that provides the ISDN service to
you.
Logical
Channels
The three available channels of a BRI connection, which are
defined not as three physically separate wires, but as three separate
ISDN system channels.
LT
Line termination. Defines the local loop at the telephone
company side of an ISDN connection to match the NT1 function at
the customer end of the local loop.
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M -
Mbps
Million bits per second.
Multi-link
PPP
Allows you to combine two or more B Channels into a single,
faster PPP connection. With Multi-link PPP, you could have a 128
kilobit/second PPP connection over a Basic Rate ISDN line. The
next releases of Windows 95 and Windows NT will include Multi-Link
PPP support.
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NANP
North American Numbering Plan. The familiar ten-digit numbering
system used today in the US., Canada, and Mexico, which includes
the three-digit area code followed by the seven-digit local telephone
number.
National
ISDN
Defined by Bellcore, National ISDN 1 (NI-1) is an agreement
among telephone companies and CPE vendors to jointly provide the
first phase of standards-based ISDN. NI-1 is a collection of standards
to allow CPE to work across different telephone company switches
using the Basic Rate Interface.
NDIS
Network Driver Interface Specification. Developed by Microsoft
NDIS provides a common set of rules for network adapter manufacturers
and network operating system (NOS) developers to use for communication
between the network adapter and the NOS. Most network adapters
now ship with an NDIS driver. If the NOS you use supports NDIS,
which most do, you can use any network adapter that has an NDIS
driver.
Network
Interface Box
The device at the point that the wires from the telephone
company and the end users wiring meet.
NI-1
(National ISDN-1)
A specification for a "standard" ISDN phone line. National
ISDN 1 is intended to be a set of standards which every manufacturer
can conform to. For example, ISDN phones that conform to the National
ISDN 1 standard will work, regardless of the central office the
customer is connected to. Note: Future standards, denoted as NI2
and NI3, are currently being developed.
NT-1
(Network Termination-1)
The device that connects to your ISDN hardware and works as
a converter between an ISDN U-interface and an ISDN S/T-Interface.
Some ISDN adapters have a NT-1 already built into them. This is
easier and less expensive than an external NT-1, but may prevent
you from connecting other equipment to your ISDN line.
NT1
Plus device
A device that includes a built-in NT1 as well as ports to
connect other devices (analog, ISDN, or X.25) to an ISDN line.
NT2
Network Termination 2. A device that handles network termination
and switching functions, typically embodied in PBXs (Private Branch
Exchanges). An NT2 device performs intelligent operations such
as switching and concentrating traffic across multiple B channels
in a PRI line.
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ODI
Open Data Interface. The specification develloped by Novell
for supporting different adapters.
Out-of-band
Signaling
Allows telephone network management signaling functions and
other service to be sent over a separate channel rather than the
bearer channel. ISDN uses out-of-band signaling via the D channel.
Out-of-band signaling used in ISDN consists of messages rather
than audio signals, as in the case with the Touch Tone analog
telephone system.
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P -
Packet
Switching
A data transmission method in which data are transferred via
packets. A packet is a block of data. Packets are sent using a
store-and-forward method across nodes in a network.
PAP
Password Authentication Protocol. A security language
that establishes a two-way handshake to verify the identity of
two computers. In PAP, passwords are sent in text format.
Passband
The frequency spectrum that determines the amount of data
that can be transmitted through a channel. The passband is what
determines the band width of a channel.
Passive
Bus
Refers to the ability to connect multiple devices to a single
BRI connection without repeaters to boost the signal. The configuration
of the passive bus combines the terminating residence for all
the devices connected to your ISDN line to add up to 100 ohms.
PBX
Private Branch Exchange. A PBX is a private telephone switch
that provides switching (including a full set of switching features)
for an office or campus. PBXs often use proprietary digital-line
protocols, although some are analog-based.
PCM
Pulse Code Modulation. The method used to convert analog audio
to digitized audio.
Point-to-Multipoint
Configuration
A physical connection in which a single network termination
supports multiple terminal equipment devices. This configuration
in supported by the S/T-interface.
Point-to-Multipoint
Connection
A connection established between one device on one end and more
than one device on the other end.
Point-to-Point
Protocol (PPP)
A protocol that allows a computer to use TCP/IP to connect
to other computers over a standard phone line using a high-speed
modem.
POTS
Plain Old Telephone Service: an analog (non-digital) telephone
line.
PPP/MP
Point-to-Point Protocol/Multilink Protocol. The new Point-to-Point
Protocol for ISDN connection that allows use of both B channel
for remote access to the Internet. PPP/MP also allows different
remote access devices to communicate with each other.
Primary
Rate Interface (PRI)
A type of ISDN service that offers 23 B channels at 64 kbs and
one D channel at 64 kbs (23B+D). In Europe, PRI provides for 30
B channels and two D channels (30B+2D).
Protector
Block
The point just before the network interface box at the demarc.
Provisioning
The combination of device and service options that make up your
ISDN line. You order your ISDN line, but the telephone company
provisions the line, i.e.-- it configures your ISDN service according
the physical capabilities of the switch, as well as the options
you choose.
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R -
R
reference point
The ISDN reference point that sits between the non-ISDN device
and the terminal adapter (TA) functional device.
Rate
Adaption
A system that allows two pieces of data equipment operating at
different data transmission rates to interoperate
RBOC
Regional Bell Operating Company. One of the local exchange carriers
that were created during the break up of AT&mpT. RBOCs provide
telephone service in a region of the U.S. They currently can't
offer long-distance telephone service between LATAs or manufacture
equipment.
Reference
Point
A specific point in the model of how ISDN works. Each component
of this model is identified using a reference point. For example,
the U reference point defines the local loop of an ISDN connection.
These reference points are also called interfaces, such as the
U-interface or S/T-interface.
Repeater
Equipment used to amplify a signal to boost the range of the
signal over larger distances.
Router
A device that connects two or more networks. A router works
like a bridge, but has greater capabilities than a bridge. A router
determines where the destination computer is located, and then
finds the best way to get there.
RJ-11
The most common telephone jack in the world, this is a six-conductor
modular jack wired with 4 wires. You probably have RJ-11 jacks
in your house.
RJ-45
An 8-pin connector jack used with standard telephone lines,
and required by some ISDN hardware. A little larger than an RJ-11
jack.
RS-232
An industry standard for serial commincations connections. ost
PC's include one or more RS-232 port for connecting devices such
as a modem or a mouse.
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S
reference point
The ISDN reference point that represents where a CPE connects
to a customer switching device, such as a PBX system. This type
of device is called an NT2 functional device.
Service
Profile Identifier (SPID)
A number or set of numbers assigned to your ISDN line by your
phone company. In the U.S., one SPID is assigned to each channel.
The switch uses SPIDs as unique identification numbers for each
ISDN line, so it can determine where to send calls and signals.
S/T-Interface
The part of the ISDN line that connects to the computer or
phone. Switch Type. The brand of equipment and software revision
level that the telephone company uses to provide you with ISDN
service. There are only a few types of switches in the world and
usually just one in countries other than the United States.
SS#7
Signaling System Number 7. A common channel signaling system
that performs network signaling functions. Used to establish ISDN
call functions.
Subscriber
Loop
The pair of copper wires that connect the end user to the telephone
network. These same wires are used to provide ISDN service but
need the addition of the NT1 at the end-user location and the
line termination at the central office.
Supplementary
Services
The collection of voice communication services available via
ISDN. These services include call management features such as
call appearances, conference calling, and call forwarding
Switch
The equipment that connects users of the telecommunications
network. Each subscriber has a dedicated loop to the nearest telephone
switch. All of these switches have access to trunk lines for making
calls beyond the local exchange area.
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T
reference point
The ISDN reference point that represents where an ISDN device
connects to an NT1 functional device.
TA
Terminal adapter. The ISDN functional device that allows non-ISDN
devices to work with ISDN.
Tariff
A rate and availability schedule for telecommunication services
that is filed with and approved by a regulatory body to become
effective. Tariffs also include general terms and conditions of
service.
TCP/IP
Transmission Control Protocol and Internet Protocol. The suite
of networking protocols that let disparate types of computers
communicate over the Internet.
TCP/IP
stack
The software that allows a computer to communicate via TCP/IP.
TE
Terminal equipment. A term for any device connected to an
ISDN line.
TEI
Terminal Equipment 1. Any ISDN ready device that connects
directly to ISDN. An ISDN telephone is an example of a TE1 device.
TE2
Terminal Equipment 2. Any non-ISDN device that must be used
with a terminal adapter to work with ISDN. An analog telephone
is an example of a TE2 device. The combination of a TE2 and a
TA has the same functionally as a TE1.
Telephony
The marriage of computer and telecommunication.
TA
TA Terminal adapter. Any device that adapts a non-ISDN terminal
for an ISDN interface. A TA gives a TE2 device the functionality
of a TE1 device.
Twisted
Pair
Another term for regular telephone wiring. Each telephone
"wire" is actually a pair of wires.
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U -
UART
Universal Asynhronous Receiver/Transmitter. UART chips are
the part of your PC's communication port that handles commincations
between the CPU and the device on that COM port.
U-interface
point
U reference point. The reference point of an ISDN connection
that includes the local loop wiring up to the NT1 functional device.
Usage
Sensitive
The cost of a service, such as ISDN or analog telephone service,
that is based on the time you actually use the service.
UPS
Uninterruptible power supply. A device that ensures a back-up
power supply for electrical devices in the event of a power outage.
For ISDN, NT1 Plus devices can include UPS for maintaining power
for analog voice communication during a power outage.
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W -
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X -
X.25
The protocol for packet-mode services as defined by CCITT.
A CCITT interface standard that lets computing devices communicate
via wide area packet-switched data networks.
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