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TUCoPS :: Phreaking Technical System Info :: mcitg1.txt

MCI Telecom Glossary Pt.1


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                                Proudly Presents

                      The MCI Telecommunications Glossary

                            Part I Volume I (A - D)

                              taken directly from

        The MCI School of Telecommunications Management Reference Guide

                         and typed by Knight Lightning


                                     - A -

A & B LEADS                            Designation of leads derived from the
                                       midpoints of the two 2-wire pairs
                                       comprising a 4-wire circuit.

ABBREVIATED DIALING                    The ability of a telephone user to
                                       reach frequently called numbers by
                                       using less than seven digits.
                                       Synonym:   Speed Dialing

ACCESS CHARGE                          A fee paid for the use of local lines.

ACCESS CODE                            A digit or number of digits required
                                       to be connected to a privat line
                                       arranged for dial access.

ACCESS LINE                            A telephone circuit which connects a
                                       customer location to a network switching

AIRLINE MILEAGE                        Calculated point-to-point mileage
                                       between terminal facilities.

ALL TRUNKS BUSY (ATB)                  A single tone interrupted at a 120 ipm
                                       (impulsess per minute) rate to indicate
                                       all lines or trunks in a routing group
                                       are busy.

ALTERNATE ROUTE                        A secondary communications path used to
                                       reach a destination if the primary path
                                       is unavailable.

ALTERNATE USE                          The ability to switch communications
                                       facilities from one type of service to
                                       another, i.e., voice to data, etc.

ALTERNATE VOICE DATA (AVD)             A single transmission facility which
                                       can be used for either voice or data.

AMERICAN STANDARD CODE FOR             An 8 level code developed for the
INFORMATION INTERCHANGE (ASCII)        interchange of information between data
                                       processing and communications systems.

ANALOG SIGNAL                          A signal in the form of a continuous
                                       varying physical quantity, e.g., voltage
                                       which reflects variations in some
                                       quantity, e.g., loudness in the human

ANNUNICATOR                            An audible intercept device that states
                                       the condition or restrictions
                                       associated with circuits or procedures.

ANSWER BACK                            An electrical and/or visual indication
                                       to the calling or sending end that the
                                       called or received station is on the

ANSWER SUPERVISION                     An off-hook signal transmitted toward
                                       the calling end of a switched
                                       connection when the called party

AREA CODE                              Synonym: Numbering Plan Area (NPA).
                                       A three digit number identifying more
                                       than 150 geographic areas of the United
                                       States and Canada which permits direct
                                       distance dialing on the telephone
                                       system. A similar global numbering
                                       plan has been established for
                                       international subscriber dialing.

ATTENDANT POSITION                     A telephone switchboard operator's
                                       position. It provides either
                                       automatic (cordless) or manual (plug
                                       and jack) operator controls for
                                       incoming and/or outgoing telephone

ATTENTUATION                           A general term used to denote the
                                       decrease in power between that
                                       transmitted and that received due to
                                       loss through equipment, lines, or
                                       other transmission devices. It is
                                       usually expressed as a ration in db

AUDIBLE RINGING TONE                   An audible signal heard by the calling
                                       party during the ringing-interval.

AUTHORIZATION CODE                     An identification number that the
                                       caller enters when placing a call
                                       which is used for billing purposes.

AUTHORIZED USER                        A person, firm, organization,
                                       corporation or any other entity
                                       authorized by the customer to send or
                                       receive communications over a specific
                                       communications network.

AUTO ANSWER                            A machine feature that allows a
                                       transmission control unit or station to
                                       automatically respond to a call that it

AUTOMATIC CALL DISTRIBUTOR (ACD)       A switching system designed to queue
                                       and/or distribute a large volume of
                                       incoming calls to a group of attendents
                                       to the next available "answering"

AUTOMATIC DIALING UNIT                 A device which automatically generates
                                       a predetermined set of dialing digits.

AUTOMATIC IDENTIFICATION OF            A computer generated report showing all
OUTWARD DIALING (AIOD)                 long distance calls placed over AT&T's
                                       toll network.

AUTOMATIC NUMBER IDENTIFICATION (ANI)  Automatic equipment at a local dial
                                       office used on customer dialed calls to
                                       identify the calling-station.

AUTOMATIC ROUTE SELECTION (ARS)        Least cost routing via AT&T CENTREX

                                     - B -

BAND                                   (1) The range of frequencies between
                                       two defined limits. (2) In reference
                                       to WATS, one of the five specific
                                       geographic areas as defined by AT&T.
                                       Synonym:   BANDWIDTH.

BANDWIDTH                              See BAND.

BASEBAND                               The total frequency band occupied by
                                       the aggregate of all the voice and
                                       data signals used to modulate a radio

BAUD                                   A unit of signaling speed. The speed in
                                       baud is the number of discrete conditions
                                       conditions or signal elements per
                                       second. If each signal event represents
                                       only one bit condition, then Baud is the
                                       same as bits per second. When each
                                       signal event represents other than one
                                       bit, Baud does not equal bits per

BELL OPERATING COMPANY (BOC) /BELL     Any of the 24 AT&T affiliated
SYSTEMS OPERATING COMPANY (BSOC)       companies providing local service.

BELL SYSTEM                            The aggregate of AT&T's 24 associated
                                       telephone companies, Long Lines,
                                       Western Electric, and Bell Labs.

BILLING NUMBER                         The MCI term for the number which
                                       identifies a customer on a billing
                                       location level, assigned to Network
                                       Service Customer (by COMS). Assigned for
                                       each unique customer name and billing
                                       location. For internal use only.

BINARY                                 A number system that uses only two
                                       characters ("0" and "1").

BIT                                    A binary digit.  The smallest unit of
                                       coded information.

BITS PER SECOND (BPS)                  The rate at which data transmission
                                       is measured.

BLOCKED CALLS                          Attempted calls that are not connected
                                       because (1) all lines to the central
                                       offices are in use; or (2) all connecting
                                       connecting paths through the PBX/switch
                                       are in use.

BLOCKED ANI                            ANI prohibited from completing a call
                                       over the MCI network.

BREAK                                  A means of interrupting transmission,
                                       a momentary interruption of a circuit.

BROADBAND                              A transmission facility having a
                                       bandwidth of greater then 20 kHz.

BUS                                    A heavy conductor, or group of
                                       conductors, to which several units of
                                       the same type of equipment may be

BUSY                                   The condition in which facilities over
                                       which a call is to be connected are
                                       already in use.

BUSY HOUR                              The time of day when phone lines are
                                       most in demand.

BUSY TONE                              A single that is interrupted at
                                       60 ipm (impulses per minute) rate to
                                       indicate that the terminal point of a
                                       call is already in use.

BYTE                                   A group of binary digits that are
                                       processed by a computer as a unit.

                                     - C -

CARRIER                                High frequency current that can be
                                       modulated with voice or digital signals
                                       for bulk transmission via cable or radio

CARRIER SYSTEM                         A system for providing several
                                       communications channels over a single

CATHODE RAY TUBE (CRT)                 The "television-like" screen used to
                                       display the output from a computer.

CELLULAR MOBILE RADIO                  A system providing exchange telephone
                                       service to a station located in an auto
                                       or other mobile vehicle, using radio
                                       circuits to a base radio station which
                                       covers a specific geographical area and
                                       as the vehicle moves from one area to
                                       another, different base radio stations
                                       handle the call.

CENTRAL OFFICE (CO)                    A telephone switching center that
                                       provides local access to the public
                                       network.  Sometimes referred to as:
                                       Class 5 office, end office, or Local
                                       Dial Office.

CENTREX, CO                            PBX Service provided by a switch located
                                       at the telephone company central office.

CENTREX, CU                            A variation on Centrex CO provided by
                                       a telephone company maintained "Central
                                       Office" type switch located at the
                                       customer's premises.

CENTRAL PRCESSING UNIT (CPU)           The control unit within a computer which
                                       handles all the intelligent functions of
                                       the systems.  In a telephone switch,
                                       directs all potions of the system to
                                       carry out their appropiate functions.
                                       Synonym: Common Control.

CHANNEL                                A communication path via a carrier or
                                       microwave radio.

CHARACTER                              Any letter, digit, or special symbol.
                                       In data transmission would be
                                       represented by a specific code made up
                                       of a group of binary digits.

CIRCUIT                                A path for the transmission of
                                       electromagnetic signals to include all
                                       conditioning and signaling equipment.
                                       Synonym:   Facility

CIRCUIT SWITCHING                      A switching system that completes a
                                       dedicated transmission path from sender
                                       to receiver at the time of transmission.

CLASS OF SERVICE/CLASS MARK (COS)      A subgrouping of telephone customers or
                                       users for the sake of rate distinction
                                       or limitation of service.

COAXIAL CABLE                          A cable having several coaxial lines
                                       under a single protective sheath.
                                       Usually used as a high capicity carrier
                                       in urban areas between interexchange and
                                       toll offices.

CODEC                                  Coder-Decoder. Used to convert analog
                                       signals to digital form for transmission
                                       over a digital median and back again to
                                       the original analog form.

COMMON CARRIER                         A government regulated private company
                                       that provides the general public with
                                       telecommunications services and

COMMON CHANNEL INTEROFFICE             A digital technology used by AT&T to
SIGNALING (CCIS)                       enhance their Integrated Services
                                       Digital Network.  It uses a seperate
                                       data line to route interoffice signals
                                       to provide faster call set-up and more
                                       efficient use of trunks.

COMMON CONTROL SWITCHING ARRANGEMENT   An arrangement for telecommunications
(CCSA)                                 networks in which common controlled
                                       switching machines are used to route
                                       traffic over network routes and access
                                       lines.  The switching machine may be
                                       shared with other users and is
                                       maintained by the telephone company.

COMPUTER PORT/TKI PORT                 The interface through which the computer
                                       connects to the communications circuit.

CONDITIONING EQUIPMENT                 Equipment modifications or adjustments
                                       necessary to match transmission levels
                                       and impedances and which equalizes
                                       transmission and delay to bring circuit
                                       losses, levels, and distortion within
                                       established standards.

CONFIGURATION                          The combination of long-distance
                                       services and/or equipment that make up a
                                       communications system.

CONTROL UNIT (CU)                      The central processor of a telephone
                                       switching device.

CORPORATE ID NUMBER                    The MCI term for the number which
                                       identifies a customer on a corporate
                                       level. (Not all MCI customers have

COST COMPONENT                         The price of each type of long distance
                                       service and/or equipment that
                                       constitutes a configuration.

COST PER HOUR (CPH)                    Total cost of different services divided
                                       by total holding time (in minutes).

CROSS CONNECTION                       The wire connections running between
                                       terminals on the two sides of a
                                       distribution frame, or between binding
                                       posts in a terminal.

CROSS TALK                             The unwanted energy (speech or tone)
                                       transferred from one circuit to another

CUSTOMER OWNED AND MAINTAINED (COAM)   Customer provided communications
                                       apparatus, and their associated wiring.

CUSTOMER PREMISE EQUIPMENT (CPE)       Telephone equipment, usually including
                                       wiring located within the customer's
                                       part of a building.

CUT                                    To transfer a sevice from one facility
                                       to another.

CUT THROUGH                            The establishment of a complete path for
                                       signaling and/or audio communications.

                                     - D -

DATA                                   Any representation, such as characters
                                       to which a meaning is assigned.

DATA COMMUNICATIONS                    The movement of coded information by
                                       means of electronic transmission

DATA SET                               A device which converts data into
                                       signals suitable for transmission over
                                       communications lines.

DATA TERMINAL                          A station in a system capable of sending
                                       and/or receiving data signals.

DECIBEL (db)                           A unit measurment represented as a ratio
                                       of two voltages, currents or powers and
                                       is used to measure transmission loss or

DELAY DIAL                             A dialing configuration whereby local
                                       dial equipment will wait until it
                                       receives the entire telephone number
                                       before seizing a circuit to transmit
                                       the call.

DELTA MODULATION (DM)                  A variant of pulse code modulation
                                       whereby a code representing the
                                       difference between the amplitude of a
                                       sample and t~he amplitude of a previous
                                       one is sent.  Operates well in the
                                       presence of noise, but requires a wide
                                       frequency band.

DEMODULATION                           The process of retrieving data from a
                                       modulated signal.

DIAL LEVEL                             The selection of stations or services
                                       associated with a PBX using a one to
                                       four digit code (e.g., dialing 9 for
                                       access to outside dial tone).

DIAL PULSING                           The transmitting of telephone address
                                       signals by momentarily opening a DC
                                       circuit a number of times corresponding
                                       to the decimal digit which is dialed.

DIAL REPEATING TIE LINE/               A tie line which permits direct station
DIAL REPEATING TIE TRUNK               to station calling without use of the

DIAL SELECTIVE SIGNALING               A multipoint network in which the called
                                       party is selected by a prearranged
                                       dialing code.

DIAL TONE                              A tone indicating that automatic
                                       switching equipment is ready to receive
                                       dial signals.

DIALING PLAN                           A description of the dialing
                                       arrangements for customer use on a

DIGITAL                                Referring to the use of digits to
                                       formulate and solve problems, or to
                                       encode information.

DIMENSION CUSTOM TELEPHONE SERVICE     AT&T's electronically programmable
(DCTS)                                 telephone station sets which use special
                                       buttons to access PBX features.

DIRECT DISTANCE DIALING (DDD)          A toll service that permits customers to
                                       dial their own long distance call
                                       without the aid of an operator.

DIRECT INWARD DIALING (DID)            A PBX or CENTREX feature that allows a
                                       customer outside the system to directly
                                       dial a station within the system.

DIRECT OUTWARD DIALING                 A PBX or CENTREX feature that allows a
                                       station user to gain direct access to
                                       an exchange network.

DROP                                   That direction of a circuit which looks
                                       towards the local operator.

DRY CIRCUIT                            A circuit which transmits voice signals
                                       and carries no direct current.

DUAL TONE MULTI-FREQUENCY (DTMF)       Also know as Touch Tone. A type of
                                       signaling which emits two distinct
                                       frequencies for each indicaated digit.

DUPLEX                                 Simultaneous two-way independent

DX SIGNALING                           A long-range bidirectional signaling
                                       method using paths derived from
                                       transmission cable pairs.  It is based
                                       on a balanced and symetrical circuit
                                       that is identical at both ends.  This
                                       circuit presents an E&M lead interface
                                       to connecting circuits.


This concludes Part 1 Volume I of the MCI Telecommunications Glossary. Look for
more G-philes from The MCI School of Telecommunications Management Reference
Guide coming soon.

                      This has been a 2600 Club production

                              Thanx to Taran King

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