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A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z
A
Access Services
Access services are specified sets of information transfer capabilities furnished to users at
telecommunications network points-of-termination (POTs) to provide access to network transport
services. Two examples are the following: subscriber access lines, the connection between a
network POT (in this case more commonly known as a Network Interface NI) and a local
exchange carrier switching system; and trunks between interexchange carrier points-of-presence
and local exchange carrier switching systems (The POT at the POP is identified as the point of
interface POI). End-to-end connections require originating and terminating access services.
Access Tandem (AT)
AT is a LEC switching system that performs concentration and distribution functions for inter-
LATA traffic originating or terminating within a LATA.
ACD
automatic call distribution
ACF
access coordination fee
Address Signals
Address Signals convey destination information such as a called 4-digit extension number, central
office code, and when required, area code and serving IXC carrier code. These signals may be
generated by station equipment, or by a switching system.
AMI
alternate mark inversion
Analog Carrier System
An analog carrier system is a transmission system that uses repeaters that compensate for
analog medium impairments, and produce output signals that are linear-scaled versions of input
signals. Analog carrier systems can carry speech, data, video and supervisory signals although
they are best suited for speech signals.
Analog Signal
An analog signal is a continuous electrical signal that varies in direct correlation with an
impressed phenomenon, stimulus, or event that bears intelligence. Sound waves and their
electrical analogs are characterized by loudness (amplitude) and pitch. Analog signals can
assume any of an infinite number of amplitude values or states within a specified range, in
accordance with or analogous to, an impressed stimulus. Pitch refers to how many times per
second the signal swings between high and low amplitudes, i.e., its frequency.
ANI
automatic number identification
ANSI
American National Standards Institute
ASB
asynchronous balanced mode
ASI
alternate space inversion
Asynchronous Transfer Mode (ATM)
ATM is a broad-bandwidth, low delay, packet-like (cell relay) switching and multiplexing
technique. It is essentially connection oriented, although it is envisioned to support all services.
ATM networks will accept or reject connections based on user's average and peak bandwidth
requirements providing flexible and efficient service for LAN-to-LAN, compressed video and other
applications that involve variable bit rate (VBR) traffic.
ATM
asynchronous transfer mode (See Asynchronous Transfer Mode).
Automatic Call Distribution (ACD)
ACD is a means for efficiently directing and managing large numbers of incoming calls to specific
departments/terminals within an organization.
AWG
American Wire Gauge.
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| B
B8ZS
bipolar eight-zero substitution
Backbone Network
A backbone network is a transmission facility designed to interconnect often lower-speed
distribution networks, channels, or clusters of dispersed terminals or devices.
Backbone Wiring
In a premises distribution system, backbone wiring is the cable connecting telecommunications
closets and equipment rooms within a building, and/or between buildings in a campus. Backbone
wiring is sometimes referred to as the riser subsystem.
Bandwidth
Bandwidth is a frequency range, usually specified by the number of hertz in a band or between
upper and lower limiting frequencies. Alternatively, the frequency range that a device is capable
of generating, handling, passing or allowing.
BFt
terminal framing bit
BF
framing bit
Binary digit
See Bit.
Binding Post
A binding post is a screw with a small nut mounted on a terminal box. Wires are joined together
by wrapping them around a screw and then tightening the nut on them.
Bipolar Signals
Bipolar signals are signals in which positive and negative pulses, always alternating, represent
one binary signal state only. The absence of pulses represents the other binary state. Bipolar has
two forms, AMI and ASI. In alternate mark inversion (AMI) the pulses correspond to ls; in
alternate space inversion (ASI) the pulses correspond to 0s.
BIPS
billion instructions per second
BISDN
broadband integrated services digital network
Bit
A bit is the most fundamental and widely used form of digital signals are binary signals, in which
one amplitude condition represents a binary digit 1, and another amplitude condition represents
a binary digit 0. Thus a binary digit, or bit is one of the members of a set of two in a numeration
system that is based on two and only two possible different values or states.
Bit Error Rate (BER)
BER is the ratio of the number of bits received with errors to the total number of bits transmitted.
BER and the average number of error-free seconds are the principal impairment measurements
for digital channels.
Bit Rate
Bit rate is the capacity characteristic of digital signals as defined by the number of bits (or bytes)
per second that a channel will support. For example, a transmission facility that can support
information exchange at the rate of I megabit per second (1 Mbps or 1,000,000 bits per second)
delivers the same quantity of information, i.e., throughput, as a 1 kilobit per second (kbps or
1,000 bits per second) facility, but, in only 1/1000 of the time.
BOC (Bell-operating Company)
BOC is the common term for one of 24 local exchange carrier telephone companies that were
part of the Bell System prior to divestiture. All but two of the BOCs (Southern New England
Telephone in Connecticut and Cincinnati Bell in Ohio) are owned and managed by one of 7
regional Bell holding companies (RBHCs). Approximately 80% of America's local exchange users
are served by the BOCs.
BOM
Bill of Materials
BOQ
Bill of Quantity
Bridge Tap
Bridge tap is an undetermined length of wire attached between the normal endpoints of a circuit
that introduces unwanted impedance imbalances for data transmission.
Bridges
In IEEE 802 local area network (LAN) standards, bridges are devices that connect LANs, or LAN
segments, at the data link layer. Bridges provide the means to extend the LAN environment in
physical extent, number of stations, performance and reliability. Bridges perform three basic
functions: frame (as opposed to packet) forwarding; learning of station addresses; and resolving
of possible loops in the topology by participating in the spanning tree algorithm. Self learning
bridges construct tables of network addresses by listening" to source address information
contained in data signal frames. Other functions include the ability to filter traffic to keep traffic
originating and terminating in one network segment from leaving that segment; restricting
specified traffic to one segment that might otherwise be routed to other segments; and collecting
and storing network management and control information obtained via traffic monitoring.
BRI
basic rate interface
Broadband Integrated Services Digital Network (BISDN)
CCITT is developing a BISDN umbrella standard, incorporating underlying standards for
integrated digital network switching, multiplexing and transmission facilities, that will be able to
meet expanding voice, data, video and other requirements well into the future. In one of the first
draft CCITT documents BISDN is simply defined as "a service requiring transmission channels
capable of supporting rates greater than the primary rate". In the U.S. the primary rate for
"narrowband" ISDN (as the current standard is sometimes referred to) is 1.544 Mbps.
Brouters
Brouters are devices that combine the functions of bridges and routers. See bridges, routers.
Bus
In digital systems, e.g., time division multiplexing equipment, a bus (also referred to as a
highway) is defined as one or more conductors (or some medium) that connect a related group
of devices.
Business Applications
Business applications are unique aggregations of telecommunications services that satisfy
particular enterprise needs.
Byte
A byte, generally, is an 8-bit quantity of information, used mainly in referring to parallel data
transfer, and data storage; also generally referred to in data communications as an octet or
character.
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| C
CAB
Carrier Access Business
Cable
A cable is a group of metallic conductors or optical fibers that are bound together, usually with a
protective sheath, a strength member, and insulation between individual conductors/fibers and
for the entire group.
CABS
Carrier Access Billing System
CALC
customer access line charges
CAP
competitive access provider
Carrier
A carrier is a local (intra-LATA) or long distance (inter-LATA) telecommunications service
providing organization. A waveform, pulsed or continuous, that is modulated by another
information bearing waveform.
Carrier System
A carrier system is a transmission system for transmitting one or more channels of information by
processing and converting to a form suitable for the transmission medium used. Carrier systems
are classified as either analog carrier systems or digital carrier systems.
CBR
continuous bit rate
CCIS
common-channel interoffice signaling
CCITT
CCITT is the International Consultative Committee for Telephone and Telegraph, a consultative
committee to the International Telecommunications Union (ITU) which recommend international
standards for telephone and telegraph services and facilities to aid international connectivity and
interoperability.
CCSA
common-control switching arrangement
CCS
centi-call seconds or common-channel signaling
CDMA
code division multiple access
Cell Relay
Call relay is the process of transferring data in the form of fixed length packets called cells. Cell
relay is used in high-bandwidth, low-delay, packet-like switching and multiplexing techniques.
The objective is to develop a single multiplexing/switching mechanism for dividing up usable
capacity (bandwidth) in a l-manner that supports its allocation to both isochronous (e.g., voice
and video traffic) as well as packet data communications services. Standards groups have
debated the optimum cell size. Small cells favor low delay for isochronous applications but involve
a higher header to user information overhead penalty than would be needed for most data
applications. The current CCITT specification for BISDN is for a 53-byte cell which includes a 5-
byte header and a 48-byte payload.
Centi Call Seconds (CCS)
CCS is a unit of the average traffic intensity of a facility during a period of time, a CCS is 100 call
seconds of traffic during one hour. Therefore a single traffic source, e.g., one call that generates
traffic 100% of the time produces 36 CCS of traffic per hour, i.e., 3600 seconds of traffic every
3600 seconds. An equivalent amount of traffic could also be generated by 10 sources that only
generate traffic 10% of the time. That is, 10 sources of traffic generating 3.6 CCS each,
contributes the same total traffic as a single 36 CCS traffic source. An alternative measure for
traffic is erlangs where 1 erlang equals 36 CCS.
CENTRal EXchange (Centrex)
Centrex is a LEC-provided switching service for business customers that permits station-to-station
dialing, listed directory number service, direct inward dialing and station number identification on
outgoing calls. The switching functions are usually performed in a central office. Digital Centrex
offers the advanced features of fourth generation PBXs, without the need to purchase or lease
equipment and, in most cases, eliminates the need for floor space, electrical prime power and
heating, ventilation and air conditioning.
Central Offices (CO)
A central office is a telephone company building in which network equipment such as switches
are installed.
Channel
A channel is a single communications path in a transmission medium connecting two or more
points in a network, each path being separated by some means; e.g., spatial or multiplex
separation, such as frequency or time division multiplexing. "Channel" and "circuit" are often
used interchangeably, however circuit can also describe a physical configuration of equipment
that provides a network transmission capability for multiple channels. The characteristics of
channels and circuits are determined by the network equipment and media used to support
them.
Channel Service Unit (CSU)
Channel Service Units (CSUs) and Data Service Units (DSUs) are required to connect digital
customer premises equipment (CPE) to carrier networks. A CSU is network channel terminating
equipment (NCTE) attaching as CPE to telephone company's digital circuits, and protecting the
network from harm. Other CSU functions include line conditioning and equalization, error control
(e.g., bipolar signal violations), and the logical ability to respond to local and network loop back
circuit testing commands. See Data Service Units (DSU).
Circuit Associated Signaling
Circuit Associated Signaling is a technique that uses the same facility path for voice and signaling
traffic. Historically this approach was selected to avoid the costs of separate channels for
signaling and because the amount of traffic generated by signaling is small compared to voice,
minimizing the chance for mutual interference. Circuit associated signaling can be contrasted with
some common-channel signaling systems that use completely separate packet switched networks
for signaling traffic.
Circuit Switching
Circuit switching is a process that establishes connections on demand and permits the exclusive
use of those connections until released. Packet and message switching, primarily used in data
communications networks are alternative switching techniques.
City Wide Digital Centrex
A city wide digital centrex is a capability to serve multiple business locations within a single NXX
(exchange code), using multiple LEC central office Centrex switches. Outside callers are unaware
that multiple business locations are involved.
CMIP
common management information protocol
Coaxial Cable
Coaxial Cable (also called coax cable or coax) consists of an insulated central conductor
surrounded by a second cylindrical conductor that is clad with an insulating sheath. The outer
conductor usually consists of copper tubing or copper braid.
COC
central office connections
Codec
Codec is a contraction of coder and decoder; a device that encodes analog signals into digital
signals, for transmission through a network in digital format, and decodes received digital signals
back into analog signals.
Common Channel Signaling (CCS)
CCS is a signaling system developed for use between stored program control digital switching
systems, in which all of the signaling information for one or more trunk groups is transmitted
over a dedicated signaling channel, usually, but not always completely separate from the user
traffic bearing facilities.
Common Management Information Protocol (CMIP)
CMIP is the OSI protocol for network management. A structure for formatting messages and
transmitting information between reporting devices (agents) and data collection programs,
developed by the International Standards Organization and designated ISO/IEC 9596.
Communications
Communications is the process of representing, transferring, interpreting or processing
information (data) among persons, places, or machines. Communications implies a sender, a
receiver, and a transmission medium over which the information travels. The meaning assigned
to the data must be recoverable without degradation.
Conditioning
Conditioning is an adjustment made to the electrical characteristics of a cable pair to improve its
performance for a specific use.
Conductor
In electrical circuits, a conductor is any material that readily permits a flow of electrons (electrical
current) through itself. Analogously, optical fibers are sometimes said to conduct light waves and
are also referred to as conductors.
Corporation for Open Systems (COS)
COS is a nonprofit organization composed of manufacturing, service, and user organizations in
the computer communications area. Seeks to facilitate the development of the international,
multi-vendor marketplace through the development, introduction, and verification of OSI and
ISDN standards and by ensuring vendor equipment interoperability.
CO
central office
CPU
central processing unit
Cross Connect
1.in a premises distribution system, equipment used to terminate and administer communications
circuits. In a wire cross connect, jumper wires or patch cords are used to make circuit
connections, between horizontal and backbone wiring segments. 2. in transmission systems a
patch panel for connecting circuits.
CSDC
circuit-switched digital capability
CSMA/CD
Carrier sense multiple access with collision detection; a local area network contention based
access control protocol technique by which all devices attached to the network "listen" for
transmissions in progress before attempting to transmit themselves and, if two or more begin
transmission simultaneously, are able to detect the "collision". In that case each backs off
(defers) for a variable period of time (determined by a preset algorithm) before again attempting
to transmit. (Defined by the IEEE 802.3 standard).
CSR
Centrex station rearrangement
CSU
channel service unit
Customer Premises Equipment
Customer Premises Equipment is all telecommunications terminal equipment located on the
customer premises. except coin operated telephones.
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| D
D type Channel Bank
A D type channel bank is channel termination equipment used for combining (multiplexing)
individual analog channel signals on a time division basis. D type channel banks provide
interfaces for "n" analog signal inputs. Each analog input signal is directed to a codec for en
coding to PCM samples. A part of a Tl carrier system.
DACS
digital access & cross-connect system
DARPA
Defense Advanced Research Projects Agency
Data Compression
Data compression is a technique that removes redundancy in transmitted bit patterns to reduce
transmission rates by 20% to 200%. For example, a modem designed to send and receive data
at 1200 bps without data compression may be capable of supporting 2400 bps with data
compression, using the same network analog voice-grade channel.
Data Service Units (DSU)
DSUs are channel service units (CSI's) and data service units (DSUs) are required to connect
digital customer premises equipment (CPE ) to carrier networks. A hardware device providing an
interface between a digital line and a unit of data terminal equipment. DSUs provide transmit and
receive control logic, synchronization and timing recovery across data circuits. DSUs may also
convert ordinary binary signals generated by CPE to special bipolar signals. Bipolar signals are
designed specifically to facilitate transmission at up to 1.544 Mbps rates over UTP cable, a media
originally intended for 3 kHz, voice bandwidth signals. See Channel Service Units (CSU).
Data Terminal Equipment (DTE)
DTE is any device that can send data, receive data or perform both functions. (Note: sometimes
DTE implies digital terminal equipment, a type of CPE used with digital Service--see CSU and
DSU.)
DB Loss
Decibel (dB) is a unit of measure of signal strength, usually the relationship between a
transmitted signal and a standard signal source. Loss is measured when the signal received
across a communication circuit is less than what was transmitted by the signal generator.
DCE
data circuit terminating equipment
DCP
digital communications protocol
DCS
digital cross-connect system
DDD
direct distance dialing
DDN
Defense Data Network
Digit L
Digital L is another amplitude condition that represents a binary digit 0. See binary digit or bit.
Digital Carrier Systems
Digital Carrier Systems are carrier systems for digital signals that uses regenerative versus linear
repeaters and time division multiplexing.
Digital Cross Connect System (DCS)
DCS is a new generation of switching/multiplex equipment that permits per-channel DS0 (64
kbps) electronic cross-connection from one T1 transmission facility to another, directly from the
constituent DSl signals. Commonly referred to as "DACS" (digital access and cross connect
system), although this is a trademark of AT&T.
Digital Signal
A digital signal is a signal (electrical or otherwise) in which information is carried in a limited
number of different (two or more) discrete states. The most fundamental and widely used form
of the digital signal is binary, in which one amplitude condition represents a binary.
Digital Termination Service (DTS)
DTS is a service provided by some carriers permitting opera tors of private networks to use
digital microwave equipment to gain access to carrier net works. The FCC has allocated a special
microwave band for DTS.
Direct Inward Dialing (DID)
DID is PBX-to-central office trunks that allow incoming calls to a PBX to ring specific stations
without attendant assistance. DID greatly reduces the number of required console attendants,
compared with systems in which all calls must be extended by console attendants.
Direct Outward Dialing (DOD)
DOD is PBX-to-central office trunks that allow outgoing calls to be placed directly by PBX stations.
Dispersion
In dispersive media, dispersion are complex signals are distorted because the various frequency
components which make up the signal have different propagation characteristics and paths. Due
to the finite conductivity of copper, wire or cable media for guided wave transmission is
fundamentally dispersive. Dispersion limits the upper bit rate that a medium can support by
distorting the signal waveforms to the extent that transitions from one information state to
another cannot be reliably detected by receiving equipment, (e.g., logical l logical 0 value
changes).
DLCI
data link connection identifier
DOD
direct outward dialing
DQDS
distributed queue dual bus
DS"N" Digital Signal Hierarchy
A time division multiplexed hierarchy of standard digital signals used in telecommunications
systems. DS1 level in the hierarchy corresponds to a 1.544 Mbps TDM signal which comprises 24
DS0 signals. DS0 refers to individual digital signals at channel rates of 64 kbps. Four DS1 signals
digitally multiplexed produce a DS2 level signal, containing 96 DS0 channels, and requires a
transmission medium that supports 6.312 Mbps. A DS3 level signal results from the digital
multiplexing of 7 DS2 signals, supports 672 DS0 signals and requires a 44.736 Mbps transmission
medium. Finally a DS4 level signal supports 6 DS3 level signals, 4032 DS0 signals and requires a
274.176 Mbps transmission medium. The DS hierarchy accounts for non synchronism in the
multiplexing plan, hence the term "asynchronous digital hierarchy" and the use of overhead bits.
Note that bit rates at higher levels are not integer multiples of 64 kbps.
DSP
digital signal processor
DSS/BLF
direct station selection/busy lamp field
DSS
digital subscriber service
DSU
data service unit
DTMF
dual tone multiple frequency
DTS
digital termination service
Dual-Tone Multiple Frequency (DTMF)
the generic name for the tone signaling scheme used to signal from telephones to switching
equipment, in which 10 decimal digits and two auxiliary characters are represented by selecting
two frequencies of the following group: 697, 770, 852, 941,1209,1336,1447 Hz.
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| E
E&M Leads Signaling
E&M Leads Signaling is an interface, used for connections between switches and transmission
systems and between transmission systems themselves. Signaling information is transferred
across the interface via 2-state voltage conditions on two leads, each with a ground return,
separate from the leads used for message information. The message and signaling information
are combined and separated by means appropriate to the transmission facility.
E-mail electronic mail
electronic mail
ECSA
Exchange Carriers Standards Assoc
EKTS
electronic key telephone system
Electrical Signal
An electrical signal is a signal consisting of an electrical current (i.e., a flow of electrons) that
varies with time or space in accordance with specified parameters.
Electronic Mail
Electronic mail is a generic term for non-interactive communication of text, data, image or voice
messages between a sender and designated recipients using telecommunications.
Electronic Switched Network (ESN) Service
ESN service is a private network service that provides user organizations with a uniform
numbering plan and numerous call-routing features. The electronic tandem switching functions
are furnished by either PBX or Centrex switching equipment.
EMI
electromagnetic interference
End Office (EO)
EO is a LEC (BOC or an ITC) switching system within a LATA where local loops to customer
stations are terminated for purposes of interconnection with each other and with trunks. CO
(central office) and EO are often used interchangeably.
Entrance Facilities
1. in a premises distribution system, the point of interconnection be tween the building wiring
system and external telecommunications facilities (LEC networks, other buildings, etc.). Bellcore
defines the interface with LEC networks as end-user points of termination (POT). 2. has a further
specific meaning in interstate access, entrance facilities for interstate access (ENFIA).
EO
end office
EPSCS
enhanced private switched communications service
Equipment Room
In a premises distribution system, an equipment room is a special purpose room(s), with access
to the backbone wiring, for housing elecommunications, data processing, security, and alarm
equipment.
erlang
An erlang is an international dimensions unit of the average traffic intensity of a facility during a
period of time; one erlang of traffic is equivalent to a single user who uses a single resource
100% of the time. See centicall seconds.
ESF
extended superframe
ESN
electronic switched network
Exchange Carrier (or local exchange carrier LEC)
An exchange carrier is any company, BOC or independent which provides intra-LATA
telecommunications within its franchised area.
Extended Superframe Format (ESF)
ESF is an extension of the superframe format of T1 carrier systems from 12 to 24 frames and the
use of framing bits for error checking, a facilities data link (FDL) as well as frame
synchronization. See superframe format.
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| F
Facilities Based Private Switched Network Services
Facilities Based Private Switched Network Services is a private network for which LECs and IXCs
dedicate physical switching and transmission facilities for the exclusive use of a particular
customer.
Fast Packet
Fast Packet is a term referring to a number of broadband switching and networking paradigms.
Implicit is the assumption of an operating environment that includes reliable, digital, broadband,
nearly error free transmission system.
FCC Federal Communications Commission
The FCC is a board of commissioners empowered by the U.S. Congress to regulate all interstate
and international communications, as well as use of the radio frequency media. www.fcc.gov
FDDI
fiber-distributed data interface
FDL
facility data link
FDM
frequency division multiplexing
FEP
front-end processor
FIPS
Federal Information Processing Standard
Foreign Exchange (FX)
FX is a service that provides a circuit(s) between a user station, a PBX, or a Centrex switch, and a
central office other than the one that normally serves the caller.
Frame
In time division multiplexing systems, Frame is a sequence of time slots each containing a sample
from one of the channels carried by the system. The frame is repeated at regular intervals,
(normally the sampling rate used in analog-to-digital conversion processes for signals being
multiplexed) and each channel usually occupies the same sequence position in successive frames.
Frame Relay
Frame relay is a network interface protocol defined in CCITT Recommendation 1.122 "Framework
for additional packet mode bearer services," as a packet mode service. In effect it combines the
statistical multiplexing and port sharing of X.25 packet switching with the high speed and low
delay of time division multiplexing and circuit switching. Unlike X.25, frame relay implements no
layer 3 protocols and only the so-called core layer 2 functions. It is a high-speed switching
technology that achieves ten times the packet throughput of existing X.25 networks by
eliminating two-thirds of the X.25 protocol complexity The basic units of information transferred
are variable length frames, using only two bytes for header information. Delay for frame relay is
lower than for X.25, but it is variable and larger than that experienced in circuit switched
networks. This means that currently frame relay is not suitable for voice and video applications
where excessive and variable delays are unacceptable.
Frequency
Frequency is acoustic waves and electrical signals might be made up of only a single tone, like a
single note on a piano. In this case the signal waveform is made up of repeating identical
"cycles" and is said to be of a single frequency, equal to the number of cycles that occur in one
second of time. In communications, frequency was traditionally expressed in cycles per second,
but is now expressed in hertz (Hz), still equal to one cycle per second. Thus, one thousand cycles
per second is equal to one thousand hertz, or a kilohertz (kHz).
Frequency Division Multiplexing (FDM)
FDM divides the frequency bandwidth (spectrum) of a broadband transmission circuit into many
subbands, each capable of supporting a single, full time communications channel on a non-
interfering basis with other multiplexed channels. FDM multiplexing is generally suitable for use
with analog carrier transmission systems.
FSS
fully separated subsidiary
FTAM
file transfer access & management
Full Duplex
Full duplex is a transmission path capable of transmitting signals in both directions
simultaneously.
FX
foreign exchange
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| G
GOSIP
Government Open Systems Interconnection Profile
Grade Of Service (GOS)
GOS is an estimate of customer satisfaction with a particular aspect of service such as noise,
echo or blocking. For example the noise grade of service is said to be 95% if, for a specified
distribution of noise, 95% of the people judge the service to be good or better. In traffic
networks, GOS defines the percentage of calls that receive no service (blocking) or poor service
(long delays). GOS measures apply to all aspects of telecommunications networks. In many cases
the literature equates GOS only with the probability of a blocked call. When used without further
explanation, GOS generally refers to blocking probability.
Ground Start
Ground start is a supervisory signal given at certain coin telephones and PBXs by connecting one
side of the line to ground.
Guided Media
Guided media is media that constrain electromagnetic or acoustic waves within boundaries
established by their physical construction. Examples include paired metallic wire cable, coaxial
cable, and fiber optic cable.
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Half Duplex
Half duplex is a transmission path capable of transmitting signals in both directions, but only in
one direction at a time.
HDLC
high-level data link control
Header
The header is control information appended to a segment of user data for control, synchronization, routing and sequencing of a transmitted data packet or frame.
Hertz (Hz)
Hertz is the measurement that distinguishes electromagnetic waveform energy; number of
cycles, or complete waves, that pass a reference point per second; measurement of frequency,
by which one hertz equals one cycle per second.
Horizontal Wiring
In a premises distribution system, horizontal wiring is the connection between the
telecommunications outlet in work areas and the telecommunications closet.
Hub
In local area networks (LANs), a hub is a wiring concentrator equipment used in hierarchical star
physical wiring topologies. Those directly connected to terminals or other user devices are of ten
referred to as local hubs or concentrators. Central hubs are those at the highest hierarchical
level. Hubs often provide the means for interconnecting 10BaseT, coaxial or fiber optic cable LAN
segments. Intelligent hubs may implement multiport bridging and network management
functions.
HVAC
heating, ventilation and air conditioning
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| I
I-MAC
isonchronous media access controller
IDN
integrated digital network
IEC
International Electrotechnical Commission
Impairments
Impairments is the (e.g., transmission channel and signal impairments) degradation caused by
practical limitations of channels, (e.g., signal level loss or attenuation, echo, various types of
signal distortion, etc.) or interference induced from outside the channel (such as power-line hum
or interference from heavy electrical machinery). The measurement of transmission impairments
is an important aspect of predicting whether or not telecommunications systems will sustain the
business applications they are intended to support. Signal-to-noise ratio, percent distortion,
frequency response, and echo are measurements that define impairments most noticeable by
users in analog voice systems.
Inbound Signaling
Inbound signaling uses not only the same channel path as the voice traffic, but the same
frequency range (band) used for the voice traffic.
Independent Telephone Company (ITC)
ITC is a local exchange carrier that is not one of the 22 divested Bell-operating companies. ITCs
are not generally subject to the restrictions of the MFJ, although some of the larger ones are
bound by separate consent decrees. Southern New England Telephone and Cincinnati Bell are
generally considered ITCs from a regulatory point of view.
Integrated Services Digital Network (ISDN)
ISDN consists of a set of standards being developed by the CCITT and various U.S. standards
setting organizations. The CCITT formal recommendations, adopted in October, 1984, first
defined ISDN as ". . . a network, in general evolving from a telephony integrated digital network,
that provides end-to-end digital connectivity to support a wide range of services, including voice
and non-voice, to which users will have access by a limited set of standard multipurpose user-
network interfaces." The concept of user access to an existing integrated digital network (IDN)
underlies the ISDN.
Inter-LATA Services
Inter-LATA services are revenues, functions, etc., that relate to telecommunications originating in
one LATA and terminating outside that LATA. An interexchange carrier (IXC) is a company which
provides telecommunications services between LATAs. (the domain of IXCs).
Intermediate Cross Connects
In a premises distribution system, intermediate cross connects are cross-connects located
telecommunications closets.
International Organization for Standardization (ISO)
ISO is a worldwide federation of national standards bodies (ISO National Bodies). The work of
preparing international standards is normally carried out through ISO technical committees. Draft
proposals for international standards adopted by the technical committees are circulated to the
National Bodies for approval before their acceptance as Draft International Standards by the
committee.
Internet
The internet is a large collection of connected networks, primarily in the United States, running
the Internet suite of protocols. Sometimes referred to as the DARPA Internet, NSF/DARPA Internet, or the Federal Research Network.
Internet suite of protocols
The internet suite of protocols is a collection of computer-communication protocols originally
developed under DARPA sponsorship, including the transmission control protocol/internet
protocol (TCP/IP).
Interoffice Channel
In LEC tariffs, Interoffice Channel is the channel connecting two serving COs (more accurately
serving wire centers). In IXC tariffs, the channel connecting two serving IXC POPs, interoffice
transmission facilities used to connect LEC switching systems.
Intra-LATA
Intra-LATA are services, revenues, functions, etc., that relate to telecommunications originating
and terminating within a single LATA (the domain of LECs).
IOC
interoffice channel
IPX
internetwork packet exchange
IP
internet protocol
ISDN
integrated services digital network
Isochronous Signals
Isochronous Signals are periodic signals in which the time interval that separates any two
corresponding significant occurrences or level transitions is always equal to some unit interval or
a multiple of that unit interval. For example, in digitized voice signals, ideally voice samples occur
isochronously at precisely the sampling interval or frame rate. Packet data signals are not
isochronous.
ISO
International Organization for Standardization
ITC
independent telephone company
ITU
International Telecommunications Union
IVR
integrated voice response
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J
JPEG
Joint Photographic Experts Group
JTM
job transfer manipulation
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K
Key Telephone System (KTS)
KTS is an arrangement of multi-line telephones and associated equipment that permits the
station user to depress buttons (keys) to access different central office or PBX lines, as well as to
perform other functions. Typical functions include answering or placing a call on a selected line,
putting a call on hold, using the intercom feature between phones at the same location, or
activating a signal buzzer.
KSU
key service unit
KTS
key telephone system
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L
LAN (IEEE 802.3 10BaseT)
LAN (Local Area Network) is an Institute of Electrical and Electronic Engineers specification for a
class of LANs using four-pair unshielded twisted pair (UTP) cable. See Local Area Network.
LAN
local area network
LATA
local access and transport area
LDN
listed directory number; generally an organization's main telephone number that appears in the
telephone book.
LDN
listed directory number
LEC
local exchange carrier
Line
See loop transmission facilities.
Local Access And Transport Area (LATA)
LATA is a geographic area (called an "exchange" or "exchange area" in the MFJ) within each
BOC's franchised area that has been established by a BOC in accordance with the provisions of
the MFJ for the purpose of defining the territory within which a BOC may offer its telecommunications services. In 1989, there were 198 LATAs, also referred to as market service
areas (MSAs), in the United States.
Local Area Network (LAN)
LAN is a premises high-speed (typically in the range of 10 Mbps) data communications system
wherein all segments of the transmission medium (typically coaxial cable, twisted pair or optical
fiber) are contained within an office or campus environment.
Local Channel
In LEC tariffs, a local channel is the local loop that connects customer premises to serving LEC
wire centers. In IXC tariffs, the network components (transmission, switching, other) used to
connect customer premises to serving IXC POPs.
Loop Length
Typically, loop length is a complete electrical circuit; the pair of wires that winds its way from the
central office to the telephone set or system at the customer's premises.
Loop Signaling
Loop signaling is a method of signaling over dc circuit paths that utilizes the metallic loop formed
by the line or trunk conductors and terminating circuits.
Loop Start
Loop start is a supervisory signal given at a telephone or PBX in response to closing the loop's DC
current path.
Loop Transmission Facilities
Loop transmission facilities connect switching systems to customer premises equipment
throughout the serving area. A loop is a transmission path between a customer's premises and a
LEC central office. The most common form of loop, a pair of wires, is also called a line. A loop"
can be derived from digital loop carrier (DLC) systems also referred to as subscriber loop carrier
(SLC) systems.
LSI
large-scale integrated circuit
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M
MAAP
maintenance & administration panels
MACSTAR
multiple access customer station rearrangement
MAC
media access control or moves, adds, and changes
Main Cross-Connects
In a premises distribution system, main cross-connects are the cross connects located in an
equipment room.
MAN
metropolitan area network
MCU
mobile control unit
Media
See transmission medium; yielded media; unguided media.
Message Telecommunications Service (MTS)
MTS is a non-private-line intrastate and interstate long-distance that uses in whole or in part the
public switched telephone network (PSTN).
MFJ
Modification of Final Judgment
MFOTS
Military Fiber-Optic Transmission System
MF
multiple frequency
MHS
message handling system
MIB
management information base
MIC
Material Identification Code
Microwave
In telecommunications, microwaves are frequencies above 1 GHz.
MIPS
million instructions per second
Modems (MOdulator/DEModulators)
Modems are devices that transform digital signals generated by data terminal equipments (DTEs)
to analog signal formats, suitable for transmission through the extensive, world-wide connectivity
of public and private, switched (dial up) and non-switched telephone voice networks.
Modification Of Final Judgment (MFJ)
MFJ is a ruling issued by U.S. District Court Judge Harold Greene which concluded the U. S.
Justice Department's antitrust suit against AT&T by modification of an earlier (1956) consent
decree's final judgment.
Modulation
Modulation is the process of varying certain parameters of a carrier signal i.e., a signal suitable
for modulation by an information signal by means of another signal (the modulating or
information bearing signal).
MPEG
Moving Pictures Experts Group
MSS
metropolitan switching system
MTSO
mobile telephone switching office
MTS
message telecommunications service
Multiline Telephone
A multiline telephone is a telephone that incorporates visual displays and switches (keys) that
permit the station user to access more than one central office or other line and to perform other
desired functions. Typical functions include answering or originating a call on a selected line,
putting a call on hold, operating an intercom feature, a buzzer, etc. Displays can indicate busy,
ringing and message waiting status.
Multimode Optical Fiber(S)
Multimode fibers, with much wider cores than single mode fibers, allow light to enter at various
angles, and reflect (bounce off of) core-clad boundaries as electromagnetic (light) wave
propagates from transmitter to receiver. From a technical performance trade-off point of view,
single mode fiber exhibits bandwidths of up to 100,000 MHz (MHz = 1,000,000 hertz or cycles
per second = one megahertz) while multimode band width is in the range of 1,000 to 2,000 MHz
(1,000 MHz = one billion hertz = one gigahertz = 1 GHz). See optical fiber(s); single
modefiber(s).
Multiplexing
Multiplexing is a technique that enables a number of communications channels to be combined
into a single broadband signal and transmitted over a single circuit. At the receiving terminal,
demultiplexing of the broadband signal separates and recovers the original channels. Multiplexing
makes more efficient use of transmission capacity to achieve a low per channel cost. Two basic
multiplexing methods used in telecommunications systems, are frequency division multiplexing
(FDM) and time division multiplexing (TDM).
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N
NBEC
non-Bell exchange carrier
NCP
network control point
NCTE
network channel terminating equipment
Network Control Point (NCP)
In virtual private networks, the Network Contol Point is a centralized database that stores a
subscriber's unique VPN definition. Highly sophisticated, this database screens every call and
applies call processing control in accordance with customer-defined requirements.
Network Operating System (NOS)
NOS is software that controls the execution of network programs and modules. Structurally,
networking software comprises multiple modules, most residing in network servers, but some
must be installed in each terminal/station that can access network resources. Peer-to-peer NOSs
permit any terminal/station to act as a resource server or a client, and can be based on
Microsoft's Disk operating system (MS DOS) designed for IBM and compatible PCs. Since MS DOS
is not designed to run multiple programs and respond to many simultaneous users, most NOSs
designed for large networks with dedicated servers/superservers, have a multitasking and multi-
user architecture. Advanced NOS products support network management, diagnostics, and
administration, as well as, primary server, client, de vice and external network driver functions.
Network Services
Network Services are specified sets of information transfer capabilities furnished to users
between telecommunications network points of termination. Network services categories include
access and transport, public and private, and switched and non-switched.
NIC
network interface card
NIST
National Institute of Standards and Technology
NI
network interface
NOC
network operations center
NOS
network operating system
NPA
numbering plan area
NSEP
National Security & Emergency Preparedness
NTSC
National Television System Committee
NT
network termination
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O
OA&M
operation administration & maintenance
OCC
other common carriers
Ohms Restriction
Ohms Restriction is the same as Ohms resistance. Ohms are measures of resistance. A resistance
of one Ohm allows one Ampere of current to pass at the electric potential of one Volt.
Open Systems Interconnection (OSI) standards
OSI standards are standards for the exchange of information among systems that are "open" to
one another by virtue of incorporating ISO standards. The OSI reference model segments
communications functions into seven layers. Each layer relies on the next lower layer to provide
more primitive functions and, in turn, provides services to support the next higher layer.
Operating Telephone Company
An operating telephone company is any Bell-operating company or independent telephone
company (termed exchange carrier in the MFJ) operating in North America.
Optical Fiber(s)
Optical fibers are light guides for electromagnetic waves in the infrared and visible light spectrum
composed of concentric cylinders made of dielectric materials with different indices of refraction
(i.e., velocity of propagation normalized to the velocity of light in free space). At the center is a
core comprising the glass or plastic strand or fiber in which a light wave travels. A low index of
refraction clad surrounds the core and is itself enclosed in a light-absorbing jacket that prevents
interference among multi-fiber cables. Multi-fiber cable can be purchased with between 2 and
136 fibers.
OPX
off-premises extension
OSC
operating system control
OSI
open systems interconnection
OSS
operations support systems or operational support system
Out Of Band Signaling
Out of band signaling uses the same channel path as the voice traffic but signaling is in a
frequency band outside that used for the voice traffic. In digital systems, out-of-band signaling
may take the appearance of an allocated bit position or a dedicated channel or time slot.
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P
P-MAC
packet media access controller
PAD
packet assembler-disassembler
PCB
printed circuit board
PDS
premises distribution system
Personal Communications
Personal communications provides at least one human operator with direct terminal access and
real time or near real time interactive communications with a remote human opera tor or an
information system resource. Personal communications can refer to a broad range of services,
systems and equipment, e.g., facsimile machines, landline telephones, cellular tele phone
systems and emerging personal communication system (PCS) adjuncts, and a variety of radio
systems including pagers, hand-held remote data entry terminals, and autonomous citizen-band-
like radio systems.
PHY
physical-layer protocol
PMD
physical-layer media-dependent
Point-of-presence (POP)
A POP is a physical location within a LATA that an IXC establishes for the purpose of gaining
access to BOC/LEC networks within the LATA using LEC provided access services. An IXC may
have more than one POP within a LATA and the POP may support public and private, switched
and non switched services.
POP
point-of-presence
POT
point of termination
PPSN
public packet switched network
Premises Distribution System (PDS)
PDS is the transmission network inside a building or among a group of buildings, for example an
office park or a campus. PDS is used in this book as a generic term although AT&T used it to
describe a specific product offering. The PDS connects desktop and other station equipment with
common host equipment, (e.g., switches, computers and building automation systems), and to
external telecommunications networks.
Private Branch Exchange (PBX)
A PBX is a premises switching system, serving a commercial or government organization, and
usually located on that organization's premises. PBXs provide telecommunications services on the
premises or campus, (e.g., internal calling and other services), and access to public and private
telecommunications network services.
Private Network
A private network is a network made up of circuits and, sometimes, switching equipment, for the
exclusive use of one organization.
PRI
primary rate interface
Protocols
Protocols are strict procedures for the initiation, maintenance and termination of data
communications. Protocols define the syntax (arrangements, formats and patterns of bits and
bytes) and the semantics (system control, information context or meaning of patterns of bits or
bytes) of exchanged data, as well as numerous other characteristics (data rates, timing, etc.).
PSN
packet switched network
PSPDN
packet switched public data network
PSTN
public switched telecommunications network
PTT
postal, telephone, and telegraph
Public Switched Telephone Network (PSTN)
A Public Switched Telephone Network (PSTN) denotes those portions of the LEC and IXC
networks that provide public switched telephone network services.
PUC
public utility commission
Pulse Code Modulation (PCM)
Pulse Code Modulation (PCM) is a modulation scheme involving conversion of a signal from
analog to digital form by means of coding. See also modulation.
PVC
permanent virtual circuit
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| Q
Quantizing Noise
In any analog to digital conversion process, e.g., PCM, quantizing noise is the difference between
the converted binary value and the actual analog signal's amplitude.
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R
RBHC
regional Bell holding company
RBS
robbed bit signaling
Regional Bell Holding Company (RBHC)
RBHC is one of 7 regional companies created by the AT&T divestiture to assume ownership of
the Bell operating companies. They are Ameritech, Bell Atlantic, Bell South, NYNEX, Pacific
Telesis, Southwestern Bell and US West.
Repeater
In digital transmission, a repeater is equipment that receives a pulse train, amplifies it, retimes it,
and then reconstructs the signal for retransmission. In IEEE 802 local area network (LAN)
standards, a repeater is essentially two transceivers joined back to back and attached to two
adjacent LAN segments. See transceiver.
RFC
request for comment
RFE
Request for Engineering
RFI
radio frequency interference
RFP
request for proposal
RF
radio frequency
Routers
In IEEE 802 local area network (LAN) standards, routers are devices that connect autonomous
networks of like architecture at the network layer (layer 3). Unlike a bridge which operates
transparently to communicating end-terminals at the logical link layer (layer 2), a router reacts
only to packets addressed to it by either a terminal or another router. Routers perform packet (as
opposed to frame) routing and forwarding functions; they can select one of many potential paths
based on transit delay, network congestion or other criteria. How routers perform their functions
is largely determined by the protocols implemented in the networks they interconnect.
RSU
remote switching unit
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S
SAFENET
survivable adaptable fiber-optic embedded network
Satellite Communications
Satellite communications entails microwave radio, line-of-sight propagation from a transmitting
earth terminal (i.e., usually ground-based but potentially ship or airborne) through the
atmosphere and outer space media to a satellite, and back to earthbound receiving terminals. In
essence, satellites are equivalent to orbiting microwave repeaters.
Scenario
In SWAT, a scenario is an iteration of an RFW project. A scenario holds the design detail work
units that are associated with the project. By creating multiple scenarios, you can compare
pricing and scheduling options. A scenario has three different statuses. A Working status
indicates that the scenario is under review. A Posted status indicates that a scenario has been
identified as the official design. A Final Posted status indicates that a scenario is the "as-built"
version of the project.
SDH
synchronous digital hierarchy
SDN
software defined network
Server
In a network, a server is equipment that makes available file, database, printing, facsimile,
communications or other services to client terminals/stations with access to the network. A
gateway is a server that permits client terminal/station access to external communications
networks and/or information systems.
Service Management System (SMS)
In virtual private networks, SMS is a facility used to build and maintain a VPN database allowing
customers to program specific functions for unique business applications. The SMS contains
complete specifications of customer defined private network specifications including location
data, numbering plan, features, screening actions, authorization codes, calling privileges, etc.
This information is downloaded (transmitted) to network control points (NCPs) which implement
its instructions on a customer-by-customer basis.
Service Order (SO)
A service order is a record that describes a customer request to establish, change, or terminate a
service. The service order contains all information required to meet a customer's needs.
SF
single frequency
Shielded Twisted Pair
Shielded twisted pair is twisted copper paired wire cable with an outer metallic sheath
surrounding insulated conductors. See unshielded twisted pair.
Signal
A signal is usually a time-dependent value attached to an energy propagating phenomenon used
to convey information, for example, an audio or sound signal in which the data is characterized in
terms of loudness and pitch.
Signaling
Signaling is the process of generating and exchanging information between components of a
telecommunications system to establish, monitor, or release connections (call handling functions)
and to control related network and system operations (other functions).
Signaling System No. 7, SS #7
SS#7 is an international common channel signaling system recommendations established by the
CCITT.
Simple Network Management Protocol (SNMP)
SNMP is the application protocol offering network management service in the Internet suite of
protocols. A structure for formatting messages and transmitting information between reporting
devices (agents) and data collection programs. Developed jointly by the Department of Defense,
industry and the academic community as part of the TCP/IP protocol suite; ratified as an Internet
standard in Request for (Comment (RFC) 1098.
Simplex
Simplex is a transmission path capable of transmitting signals in only one direction.
Single Mode Optical Fiber(s)
Single mode optical fibers have sufficiently small core diameters in relation to the wavelength
(frequency) of operation that electromagnetic (light) wave is constrained to travel in only one
transverse path from transmitter to receiver. This requires the utmost in angular alignment of
light emitting devices at points where light enters the fiber and results in higher
transmitter/termination costs than multimode fiber systems. See multimode optical fiber(s).
SMDR
station message detail record
SMDS
switched multimegabit data system
SMT
station management technology
SNA
Systems Network Architecture
SNI
subscriber network interface
SNMP
Simple network management protocol. See Simple Network Management Protocol (SNMP).
SO
Service Order
SONET
synchronous optical network
Space Division
Space division is a switch that implements the switch matrix using a physical, electrical, spatial
link. Where older space division switches used electro-mechanical mechanisms with metallic
contacts, modern space-division switches are implemented electronically using integrated circuits.
(Usually denoted by "S" in combined time and space division switches).
Special Services
Special services are any of a variety of LEC and IXC switched, non-switched, or special rate
services that are either separate from public telephone service or contribute to certain aspects of
public telephone service. Examples include PBX tie trunks, foreign exchange (FX) and private line
services. These services are important to business telecommunication planners/users.
SSN
switched service network
SS
signaling system
Station Equipment
Station equipment is a component of telecommunications systems such as a telephone or data
terminal, generally located on the user's premises. Its function is to transmit and receive user
information (traffic), and to exchange control information with the network to access
communications services.
STM
synchronous transfer mode
STP
shielded twisted pair or signaling transfer/point
Superframe Format (SF)
Superframe format is a framing format (D3/D4--mode 3), the most widely used T1 carrier
framing format in which the bipolar bit stream is organized into superframes each consisting of
12 frames. To ensure timing, the signal must consist of at least one "1" bit in every 15 bits and at
least :3 " 1" bits in every 24 bits. See extended superframe.
Supervisory Signals
Supervisory signals are signals used to indicate or control the states of circuits involved in a
particular switched connection. A supervisory signal indicates to equipment, to an operator, or to
a user that a particular state in the call has been reached and may simplify the need for action.
Switch Matrices
Switch matrices are the mechanism that provides signal paths between its input and output
terminations. Modern matrices are electronic and involve either time or space division switching.
A time division switch employs a TDM process, in a time-slot interchange (TSI) arrangement. In
space division, a physical, electrical, spatial link is established through the switch matrix.
Whereas older space division switches used electro-mechanical mechanisms with metallic
contacts, modern space-division switches are implemented electronically using integrated circuits.
Switching
Switching refers to the process of connecting appropriate lines and/or trunks to form a desired
communications path between two station sets, or more generally, any two arbitrary points in a
telecommunications network. Included are all kinds of related functions such as signaling,
monitoring the status of circuits, translating address to routing instructions, alternate routing,
testing circuits for busy conditions, and detecting and recording troubles.
Switching Systems
Switching systems are interconnect transmission facilities at various network locations and route
traffic through a network.
Systems (Manual Circuits)
In Plant Records and Assignment, these terms refer to circuits whose network elements have
been assigned manually rather than by automatic assignment.
Systems Network Architecture (SNA)
SNA is IBM's proprietary description of the logical structure, formats, protocols, and operational
sequences for transmitting information units through and controlling network configuration and
operation.
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T
T1 Carrier
A T1 carrier is a time-division multiplexed digital transmission facility capable of supporting 24
voice channels, (each encoded as a 64 kbps PCM DS0 signal), producing an aggregate
multiplexer output signal at the 1.544 Mbps DS1 rate. Developed in the 1960s, the T1 carrier is
designed to operate full duplex over two pairs in unshielded twisted pair (UTP) cable.
Tandem Switching System
A tandem switching system is a broad functional category describing systems that connect trunks
to trunks, and route traffic through a network.
Tariff
A tariff is a published rate for a specific telecommunications service, equipment, or facility that
constitutes a public contract between the user and the telecommunications supplier (i.e., carrier);
tariff services and rates are established by and for telecommunications common carriers in a
formal process in which carriers submit filings for federal or state government regulatory review,
public comments, possible amendment, and approval.
TA
terminal adapter
TCP/IP
Transmission control protocol/internet protocol. TCP/IP is the transport layer and Internet layer,
respectively, of the Internet suite of protocols. TCP corresponds to layer 4 of the OSI protocol
stack: IP performs some of the functions of layer 3. It is a connectionless protocol used primarily
to connect dissimilar networks to each other.
TCP
transmission control protocol
TDMA
time division multiple access
TDM
time division multiplexing
Telecommunications
Telecommunications is any process that enables one or more users to pass to one or more other
users information of any nature delivered in any usable form, by wire, radio, visual, or other
electrical, electromagnetic, optical means. The word is derived from the Greek tele, "far off," and
the Latin communicare "to share."
Telecommunications Closet
In a premises distribution system, a telecommunications closet is an area for connecting the
horizontal and backbone wiring and for containing active or passive PDS equipment.
Telecommunications Network
A telecommunications network is a system of interconnected facilities designed to carry traffic
from a variety of telecommunications services. The network has two different but related
aspects. In terms of its physical components, it is a facilities network. In terms of the variety of
telecommunications services that it provides, it can support a set of many traffic networks, each
representing a particular interconnection of facilities.
Telecommunications Service
Telecommunications service is a specified set of information transfer capabilities provided to a
group of users by a telecommunications system.
Terrestrial Microwave Radio
Terrestrial microwave radio is a transmission systems consisting of at least two radio
transmitter/receivers (transceivers) connected to high gain antennas (directional antennas which
concentrate electromagnetic or radiowave energy in narrow beams) focused in pairs on each
other. The operation is point-to-point, that is, communications are established between two and
only two antennas (installations) with line-of-sight visibility. This can be contrasted to point-to-
multipoint systems like broadcast radio or television.
TIA
Telecommunications Industry Association
Time Division Multiplexing (TDM)
Time Division Multiplexing is a transmission facility shared in time (rather than frequency), i.e.,
signals from several sources share a single channel or bus by using the channel or bus in
successive time slots. A discrete time slot or interval is assigned to each signal source.
Time Division Switch
A time division switch is a switch that implements the switch matrix using the TDM process, in a
time-slot interchange (TSI) arrangement (usually denoted by T in combined time and space
division switches).
Token Passing Bus LAN (IEEE 802.4)
A token passing bus LAN is a LAN using a deterministic access mechanism and topology in which
all stations actively attached to the bus "listen" for a broadcast token or supervisory frame.
Stations wishing to transmit must receive the token before doing so; however the next logical
station to transmit may not be the next physical station on the bus. Access is controlled by pre-
assigned priority algorithms.
Token Passing Ring LAN (IEEE 802.5)
A token passing ring LAN is a LAN using a deterministic access mechanism and topology, in
which a supervisory frame (or token) is passed from station to adjacent station sequentially.
Stations wishing to transmit must wait for the "free" token to arrive before transmitting data. In a
token ring LAN the start and end points of the medium are physically connected, leading to a ring
topology.
TP
transaction processing
Tracking
Tracking features user-defined approval levels and project milestone tables to generate project
cost and status information, which is tracked for reporting and review. As assigned tasks are
completed, supervisors make daily entries identifying the number of hours worked on a task,
materials used, and the number of work units completed. This information is then available for
project jeopardy tracking, cost tracking, and determination of contractor payments due.
Traffic
Traffic is the flow of information within a telecommunications network.
Transceiver
A transceiver is a generic term describing a device that can both transmit and receive. In IEEE
802 local area network (LAN) standards, a transceiver consists of a transmitter, receiver, power
converter, and, for CSMA/CD LANs, collision detector and jabber detector capabilities. The
transmitter receives signals from an attached terminal's network interface card (NIC) and
transmits them to the coaxial cable or other LAN medium. The receiver receives signals from the
medium and transmits them via the transceiver cable and NIC to the attached terminal. The
jabber detector is a timer circuit that protects the LAN from a continuously transmitting terminal.
Transfer Mode
Transfer mode is a generic term for switching and multiplexing aspects of broadband integrated
services digital networks (BISDN), adopted by CCITT Study Group XVIII.
Transmission control protocol/internet protocol (TCP/IP)
See "Internet suite of protocols" and "TCP/IP".
Transmission Facilities
Transmission facilities provide the communication paths that carry user and network control
information between nodes in a network. In general, transmission facilities consist of a medium
(e.g., free space, the atmosphere, copper or fiber optic cable) and electronic equipment located
at points along the medium. This equipment amplifies (analog systems) or regenerates (digital
systems) signals, provides termination functions at points where transmission facilities connect to
switching systems, and may provide the means to combine many separate sets of call
information into a single "multiplexed" signal to enhance the transmission efficiency.
Transmission Impai | | |
