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TUCoPS :: Phreaking Technical System Info :: mcitg2.txt

MCI Telecom Glossary Pt.2

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                                Proudly Presents

                      The MCI Telecommunications Glossary

                            Part I Volume II (E - N)

                      Typed and Edited by Knight Lightning


                                    - E -

ECHO                                  A signal that has been reflected or
                                      otherwise returned with sufficient
                                      magnitude and delay to be percieved by
                                      the speaker.

ECHO RETURN LOSS (ERL)                The loss which must be in the echo path
                                      to reduce echo to a tolerable amount.

ECHO SUPRESSOR                        A device which detects speech signals
                                      transmitted in either direction on a
                                      four-way circuit, and introduces loss
                                      in the direction of transmission.

EIGHT HUNDRED SERVICE (800)           A commonly used reference for inward WATS
                                      service (See WATS, Inward).

EITHER END HOP OFF (EEHO)             Uses either Head Hop Off or Tail End Hop

ELECTRONIC DATA PROCESSING            The use of electronic memories to store,
                                      up-date, read, and use information.

ELECTRONIC KEY TELEPHONE SETS (EKTS)  A generic term indicating key telephones
                                      with special buttons which are
                                      electronically programmed to access
                                      various PBX features.

ELECTRONIC SWITCHING SYSTEM (ESS)     A Bell System term for electronic

ELECTRONICALLY PROGRAMMABLE READ      Memory which is initially programmed by
ONLY MEMORY (EPROM)                   the manufacturer.  Changes can be made to
                                      conform to the customer requirements
                                      at their premises.

ELECTRONIC TANDEM NETWORK (ETN)       1. A private network automatically and
                                      electronically connecting the calling
                                      office to the called office through
                                      Tandem-Tie-Trunks. The network switches
                                      also function as PBX's. 2. An AT&T
                                      product name. 3. Used as a generic term
                                      a PBX base network.

END OFFICE CONVERSATION               When an end office offers equal access.

ENHANCED PRIVATE SWITCHED             A private network utilizing Bell provided
COMMUNICATIONS SERVICE (EPSCS)        equipment located in the central office
                                      and dedicated to a specific customer.

E&M LEADS                             A pair of leads which carry signals
                                      between trunk equipment and seperate
                                      signaling equipment unit.  The M lead
                                      transmits battery or ground signals to
                                      the signaling equipment, and the E lead
                                      recieves open or ground signals from the
                                      signaling equipment.

E&M SIGNALING                         An arrangement whereby signaling between
                                      a trunk circuit and an associated
                                      signaling unit is effected over two
                                      leads providing full-time, 2-way,
                                      2-level supervision.

ENTERPRISE NUMBER                     A unique telephone exchange number that
                                      permits the called party to be
                                      automatically for the incoming calls.
                                      Synonym: "Toll Free Number;" INWARD WATS.

EQUALIZATION                          The procedure of compensating for
                                      fluctuation in circuit amplitude, delay,
                                      or distortion.

ERLANG                                A unit of traffic intensity. One Erlang
                                      is the intensity at which one traffic
                                      path would be countinuously occupied,
                                      e.g., one call per hour.

ERLANG B TABLE                        A method for determining grade of service
                                      for a specified amount of traffic.
ERROR RATE                            The probability of an error ocurring
                                      during the transmission of a message.

EXCHANGE                              A telephone switching center.

EXCHANGE AREA                         A geographical unit established within a
                                      telephone company's serving area for the
                                      adminastration of telephone service
                                      provided. One schedule of charges applies
                                      to the whole area. Usually served by one
                                      or more central offices and their
                                      associated outside plant.

EXCAHNGE NETWORK FACILITIES FOR       AT&T's pricing arrangement for local
INTERSTATE ACCESS (ENFIA)             loops offered to OCCs for connecting the
                                      OCC's network to the local telephone
                                      company's central office.

EXPECTED MEASURED LOSS (EML)          The calculated 1 kH  loss of the trunk
                                      shown on the circuit or design layout

EXTENDED AREA SERVICE (EAS)           A telco tariff giving customers the
                                      option whereby the subscriber can pay a
                                      higher flat rate in order to obtain
                                      geographic coverage without additional
                                      per-call charges (non-toll charges).

                                    - F -

FACILITY                              Synonym: Circuit.

FACSMILE                              The transmission of pictures, maps or
                                      other documents via communications
                                      circuits using a device which scans the
                                      original document, transforms the image
                                      into coded signals and repoduces the
                                      original document at a distant point.

FEDERAL COMMUNICATIONS COMMISON (FC)  The government agency established by the
                                      Communications Act of 1934 which
                                      regulates the interstate communications

FIBER OPTICS                          High speed transmisson using light to
                                      send images ( in telecommunications:
                                      voice or data ) through a flexible bundle
                                      of glass fibers.
FOREIGN EXCHANGE LINES (FX)           A special access hardwire circuit that
                                      provides service between a telephone at a
                                      customer's location and a distant central

FOUR WIRE CIRCUIT                     A communications path which employs two
                                      separates electrical paths one recieving
                                      and one transmitting.

FREQUENCY                             The number of complete cycles per unit of

FREQUENCY DIVISION MULTIPLEXING (FD)  The division of an available frequency
                                      into bands.  This modulation technique
                                      requires the derived channels, each to
                                      have their own baseband and that
                                      "guardbands" be provided between channels
                                      to minimize interference or crosstalk
                                      from adjacent channels.

FREQUENCY RESPONSE                    The reaction of frequencies to the
                                      circuit components.

FULL DUPLEX                           A circuit which allows transmission of a
                                      message in both directions at the same

FULL PERIOD                           The condition of a switching system where
                                      each input a switching stage has access
                                      to every output from the stage.

                                    - G -

GRADE OF SERVICE                      The probability of a call being blocked
                                      by busy trunks, expressed as a decimal
                                      fraction, and usually meaning the
                                      busy-hour probability.

GROUP                                 12 circuits processed as a unit in a
                                      carrier system.

                                    - H -

HALF DUPLEX                           A circuit for transmitting or receiving
                                      signals in one direction at a time.

HANDSET                               That portion of the telephone containing
                                      hand-held when the telephone is in use.

HARDWARE                              Physical equipment or components of a
                                      computer system rather than a programmed
                                      method use.

HARDWIRE                              To wire or cable directly between units
                                      of equipment.

HARMONIC                              The full multiple of a base frequency.

HARMONIC DISTORTION                   The ratio, expressed in decibels, of the
                                      power at the fundamental frequency, to
                                      the power of a harmonic of that

HEAD END HOP OFF (HEHO)               A method of traffic engineering whereby
                                      calls are completed by using long
                                      distance facilities directly off the
                                      switch that serves that location.

HERTZ (Hz)                            International standard unit of frequency.
                                      Replaces, and is identical to, the order
                                      unit "Cycles-per-second."

HOMING                                Returning to the starting position, as in
                                      a rotary stepping switch.

HOOKSWITCH                            The device on which the telephone
                                      receiver hangs or on which a telephone
                                      handset hangs or rests when not in use.
                                      The weight of the reciever or handset
                                      operates a switch which opens the
                                      telephone circuit, leaving only the bell
                                      connected to the line.

HOT-CUT                               Virtually instantaneous replacement of
                                      one line with another.

HYBRID                                An electronic circuit which performs the
                                      wire conversations necessary for the
                                      connection of a local loop with a
                                      long-haul facility.

                                    - I -

INTERCEPT                             To stop a telephone call directed to an
                                      improper telephone number, and redirect
                                      that call to an operator or a recording.
INTERCONNECT                          1) The arrangement that permits the
                                      connection of customer's telecommunica-
                                      tions equipment to a communications
                                      common carrier network. 2) The industry
                                     name for manufacturers, excluding the
                                      Bell system, which provide CPE telephone

INTER-EXCHANGE MILEAGE (IXC)          The airline mileage between two cities.
                                      Synonym: Long Haul Mileage.

INTEREXCHANGE PLANT                   The facilities between the subscriber
                                      switching center and another switching

INTERFACE                             The junction or point of interconnection
                                      between two systems or equipment having
                                      different characteristics.

INTERFERENCE                          Any unwanted noise or crosstalk on a
                                      communications circuit which acts to
                                      reduce the intelligibilty of the desired
                                      signal or speech.

INTER-MACHINE TRUNK (IMT)             A circuit which connects two automatic
                                      switching centers.

INTER-OFFICE TRUNK (IOT)              A direct trunk between local exchange

INTERNATIONAL RECORD CARRIER (IRC)    Companies that handle the intra-U.S.
                                      portion of international record

INTERSTATE                            Any connection made between two states.

INTRASTATE                            Anyconnection made that remains within
                                      the boundaries of a single state.

                                    - J -

JACK                                  A connecting device having springs which
                                      make electrical contact with mating
                                      contacts of a plug.

JITTER                                Short term instability of the amplitude
                                      and/or phase of a signal.
                                      Commonly called: PHASE JITTER.

                                    - K -

KEYSET                                Muti-push button keys located on a
                                      telephone which may be punched in
                                      sequence for sending telephone number
                                      desired, precedence, or routing signals.

KEY SYSTEM                            The equipment utilized to provide the
                                      features associated with key sets.

                                    - L -

LEASED LINES                          Any circuit or combination of circuits
                                      designated to be at the exclusive
                                      disposal of a given subscriber.
                                      Synonym:  Private Line.

LEAST COST ROUTING (LCR)              A method of automatically selecting the
                                      least costly facility for transmission of
                                      a call.
                                      Synonym: Most Economical Route Selection
                                      (MERS): Route Optimization.

LEVEL                                 An expression of the relative signal
                                      strength at a point in a communications
                                      circuit compared to a standard.

LOADING                               A system for adding regularly spaced
                                      inductance units to a circuit to improve
                                      its transmission characteristics.

LOCAL ACCESS AND TRANSPORT AREA       Defines the local calling area as
(LATA)                                established by the court ordered AT&T
                                      divestiture plan.

LOCAL AREA NETWORK (LAN)              Intraoffice communication system usually
                                      used to provide data transmission in
                                      addition to voice transmission.

LOCAL LOOP                            The local connection between the end user
                                      and the Class 5 central office.

LONG HAUL                             Circuits spanning considerable distances.

LOOP BACK                             A method of performing transmission tests
                                      on a circuit not requiring the assistance
                                      of personnel at the distant end.

                                      use the metallic loop formed by the trunk
                                      conductors and the terminating equipment

                                    - M -

MAIN DISTRIBUTION FRAME (MDF)         The point where outside plant cables
                                      terminate and from which they cross
                                      connect to terminal or central office
                                      line equipment.

MAIN PBX                              A PBX directly connected to a switch via
                                      an access trunk group.

MANUAL TIE LINE                       A tie line which requires the assistance
                                      of an attendant at both ends of the
                                      circuit in order to complete a call.

MASTER GROUP (MG)                     240 circuits processed as a unit in a
                                      carrier service.

MESSAGE TELEPHONE SERVICE (MTS)       AT&T's tariffed pricing name for long
                                      distance telephone calls.

MESSAGE UNIT (MU)                     A local toll rate calling plan which is
                                      time and distance sensitive.

METAL OXIDE SEMICONDUCTOR (MOS)       A type of computer memory utilizing 1/4
                                      inch square slices of silicon.  These
                                      silicon slices require constant electric
                                      current for the data to be retained.

MICROWAVE (M/W)                       Radio transmission using very short
                                      lengths , corresponding to a frequency of
                                      1,000 megahertz or greater.
                                      Synonym:  Microwave Radio.

MICROWAVE RADIO                       Synonym: Microwave.

MODEM                                 A device which modulates and demodulates
                                      signals on a carrier frequency and allows
                                      the interface of digital terminals with
                                      analog carrier systems.

MODULATION                            Alterations in the characteristics of
                                      carrier waves.  Usually impressed on the
                                      amplitude and/or the frequency.

MONITORING DEVICE                     Records data on calls placed through a
                                      length of calls, calling location.

MOST ECONOMICAL ROUTE SELECTION       Synonym: Least Cost Routing

MULTIPLEXING                          The act of combining a number of
                                      individual message circuits for
                                      transmission over a common path.  Two
                                      methods are used: (1) frequency division,
                                      and (2) time division.

                                    - N -

NETWORK                               A collection of switches connected to one
                                      another by transmission facilities.

NETWORK NUMBERING EXCHANGE (NNX)      The three digit location code
                                      representing the central office.  "N" may
                                      be any number between "2" and "9" and "X"
                                      may be any number.

NETWORK TRUNKS                        Circuits connecting switching centers.

NODE                                  A terminal of any branch of a network.

NON-BLOCKING                          A switching network having a sufficient
                                      number of paths such that a subscriber
                                      originating a call can always reach any
                                      other idle subscriber without
                                      encountering a busy.

NUMBERING PLAN AREA (NPA)             A geographical division within which no
                                      two telephones will have the same 7 digit
                                      number.  "N" is any number between "2"
                                      and "9"; "P" is always "1" or "0"; and
                                      "A" is any number excluding "10."


This concludes Part I Volume II of the MCI Telecommunications Glossary. Look for
More G-philes on MCI by Knight Lightning coming soon to Metal Shop!

                      This has been a 2600 Club production

                              Thanx to Taran King

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