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Proudly Presents
The MCI Telecommunications Glossary
Part I Volume II (E - N)
Typed and Edited by Knight Lightning
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- 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
Off.
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
record.
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
industry.
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
office.
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
time.
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
time.
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
fundamental.
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
equipment.
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
center.
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
offices.
INTERNATIONAL RECORD CARRIER (IRC) Companies that handle the intra-U.S.
portion of international record
transmission.
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
bridges.
- 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
(MERS)
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."
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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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