Telecom Acronyms

In this artciles you will find more than hundred Telecom related Acronyms and Abbreviations.

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

ABBREVIATED DIALING   (AD)
     Preprogramming of a caller's phone system or long distance
     company's switch to recognize a 2- to 4-digit number as an
     abbreviation for a frequently dialed phone number, and
     automatically dial the whole number.
     Synonym:  Speed Dialing. ++
 
ACCESS CHARGE   (AC)
     Monies collected by local phone companies for use of their
     circuits to originate and terminate long distance calls.
     Can be per minute fees levied on long distance companies,
     Subscriber Line Charges (SLCs) levied directly on regular
     local lines, fixed monthly fees for special telco circuits
     (ie. WAL, DAL,T-1), or Special Access Surcharge (SAS) on
     special access circuits. ++
 
ACCESS LINE   (AL)
     A telephone circuit which connects a customer location to a
     network switching center. ++
 
AIRLINE MILEAGE  (AM)
     Calculated point-to-point mileage between terminal
     facilities. ++
 
ALL TRUNKS BUSY (ATB) A single tone interrupted at a 120 ipm
     (impulses per minute) rate to indicate all lines or trunks
     in a routing group are busy. ++
 
ALTERNATE ROUTE   (AR)
     A secondary communications path used to reach a destination
     if the primary path is unavailable. ++
 
ALTERNATE USE     (AU)
     The ability to switch communications facilities from one
     type 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. ++
 
ANALOG SIGNAL  (AS)
     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 voice. ++
 
ANNUNCIATOR    (AN)
     An audible intercept device that states the condition or
     restrictions associated with circuits or procedures. ++
 
ANSWER BACK    (AB)
     An electrical and/or visual indication to the calling or
     sending end that the called or received station is on the
     line. ++
 
ANSWER SUPERVISION  (AS)
     An electrical signal fed back up the line by the local
     telephone company at the distant end of a long distance call
     to indicate positively the call has been answered by the
     called party.  Tells billing equipment to start timing the
     call. ++
 
AREA CODE   (AC)
     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.
     Synonym:  Numbering Plan Area (NPA). ++
 
ATTENDANT POSITION   (AP)
     A telephone switchboard operator's position. It provides
     either automatic (cordless) or manual (plug and jack)
     operator controls for incoming and/or outgoing telephone
     calls. ++
 
ATTENTUATION   (AT)
     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 ratio in dB (decibel). ++
 
AUDIBLE RINGING TONE  (ART)
     An audible signal heard by the calling party during the
     ringing-interval. ++
 
AUTHORIZATION CODE    (AC)
     A 5- to 14-digit number entered using a touch-tone phone to
     identify the caller as a customer of the long distance
     service. Used primarily before Equal Access as a way to
     verify the caller as a customer and bill calls. ++
 
AUTO ANSWER   (AA)
     A machine feature that allows a transmission control unit or
     station to automatically respond to a call that it receives. ++
 
AUTOMATIC CALL DISTRIBUTOR (ACD)
     A switching system designed to queue and/or distribute a
     large volume of incoming calls to a group of attendants to
     the next available "answering" position. ++
 
AUTOMATIC DIALING UNIT   (ADU)
     A device which is programmed with frequently called numbers.
     The caller presses one to three digits and the preprogrammed
     number is automatically dialed into the phone circuit. ++
 
AUTOMATIC IDENTIFICATION OF OUTWARD DIALING (AIOD)
     The ability of some centrex units to provide an itemized
     breakdown of charges (including individual charges for toll
     calls) for calls made by each telephone extension. ++
 
AUTOMATIC NUMBER IDENTIFICATION (ANI)
     On long distance calls, the process by which the local phone
     company passes a caller's local billing phone number to
     his/her long distance company when a "1+" or "10-XXX" call
     is made.  With ANI a caller's long distance carrier knows
     who (what phone number) to bill without requiring the caller
     to enter any extra digits to be identified. ++
 
AUTOMATIC ROUTE SELECTION (ARS)
 
     Synonym:  Least Cost Routing   ++
 
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 the carrier.
     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
     carrier. ++
 
BAUD
     A unit of signaling speed. The speed in Baud is the number
     of discrete conditions or signal elements per second. If
     each signal event represents only one bit condition, then
     Baud is the same as bits per second. Baud does not equal
     bits per second. ++
 
BLOCKED CALLS
     Attempted calls that are not connected because (1) all lines
     to the central offices are in use; or (2) all connecting
     paths through the PBX/switch are in use. ++
 
BREAK
     A means of interrupting transmission, a momentary
     interruption of a circuit. ++
 
BREAKEVEN POINT   (BP)
     Level of usage at which the total cost of a service with a
     high fixed up-front monthly fee but low minute costs becomes
     equal to the total cost of another service with low (or
     zero) monthly fee but relatively high per minute cost. At
     usage levels higher than breakeven, the service with the
     high monthly fee is cheaper. ++
 
BROADBAND
     A transmission facility having a bandwidth of greater than
     20 kHz. ++
 
BUS
     A heavy conductor, or group of conductors, to which several
     units of the same type of equipment may be connected. ++
 
BUSY    (BY)
     The condition in which facilities over which a call is to be
     transmitted are already in use. ++
 
BUSY HOUR  (BH)
     The time of day when phone lines are most in demand. ++
 
BUSY TONE   (BT)
     A single tone that is interrupted at 60 ipm (impulses per
     minute) to indicate that the terminal point of a call is
     already in use. ++
 
BYPASS   (BP)
     The direct connection to customer-premises equipment by an
     IC. This occurs when an IC connects its own facilities (or
     facilities leased from a non-BOC entity) directly to an end
     user's premises, circumventing the use of the BOC network. ++
 
CARRIER
     A long distance company which uses primarily its own
     transmission facilities, as opposed to resellers which lease
     or buy most or all transmission facilities from carriers.
     Many people refer to any type of long distance company,
     whether it has its own network or not, as a carrier, so the
     term is not as restrictive as it used to be. ++
 
CARRIER ACCESS CODE (CAC)
     The sequence an end user dials to obtain access to the
     switched services of a carrier.  Carrier Access Codes for
     Feature Group D are composed of five digits, in the form
     10XXX, where XXX is the Carrier Identification Code. ++
 
CARRIER COMMON LINE CHARGE (CCLC)
     A per minute charge paid by long distance companies to local
     phone companies for the use of local public switched
     networks at either or both ends of a long distance call. ++
     This charge goes to pay part of the cost of telephone poles,
     wires, etc. ++
 
CARRIER IDENTIFICATION CODE (CIC)
     The three-digit number that uniquely identifies a carrier.
     The Carrier Identification Code is indicated by XXX in the
     Carrier Access Code. The same code applies to an individual
     carrier throughout the area served by the North American
     Numbering Plan. ++
 
CARRIER SYSTEM    (CS)
     A system for providing several communications channels over
     a single path. ++
 
CELLULAR MOBILE RADIO   (CMR)
     A high capacity land mobile radio system in which an
     assigned frequency spectrum is divided into discrete
     channels that are assigned to a cellular geographic serving
     area. ++
 
CENTRAL OFFICE (CO)
     With local telephone companies, the nearby building
     containing the local telco switch which provides local
     telephone service.  Also the physical point where calls
     enter the long distance 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. ++
 
CHANNEL
     A communications path via a carrier or microwave radio. ++
 
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    (COAX)
     A cable with a solid outer shield, a space and then a solid
     inner conductor.  The electromagnetic wave travels between
     the outer shield and the conductor. It can carry a much
     higher band width than a wire pair. ++
 
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   (CC)
     A government regulated private company that provides the
     general public with telecommunications services and
     facilities. ++
 
COMMON CHANNEL INTEROFFICE SIGNALING (CCIS)
     A digital technology used by AT&T to enhance their
     Integrated Services Digital Network. It uses a separate
     data line to route interoffice signals to provide faster
     call set-up and more efficient use of trunks. ++
 
COMMON CONTROL SWITCHING ARRANGEMENT (CCSA)
     The use of carrier switches under a carrier's control as
     part of a customer's private network.  The carrier's
     software controls and switches the customer's calls over
     private lines the customer has rented.  Control of the
     switch and switching functions is done in common for all
     users using the software and switching system. ++
 
CONDITIONING EQUIPMENT   (CE)
     Equipment modifications or adjustments necessary to match
     transmission levels and impedances and which equalize
     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. ++
 
COST COMPONENT   (CC)
     The price of each type of long distance service and/or
     equipment that constitutes a configuration. ++
 
CROSS CONNECTION  (CC)
     The wire connections running between terminals on the two
     sides of a distribution frame, or between binding posts in a
     terminal. ++
 
CROSS TALK    (CT)
     The unwanted energy (speech or tone) transferred from one
     circuit to another circuit. ++
 
CUSTOMER ACCESS LINE CHARGE (CALC)
     The FCC-imposed monthly surcharge added to all local lines
     to recover a portion of the cost of telephone poles, wires,
     etc. from end users.  Before deregulation, a large part of
     these costs were financed by long distance users in the form
     of higher charges. ++
 
CUSTOMER OWNED AND MAINTAINED (COAM)
     Customer provided communications apparatus and associated
     wiring. ++
 
CUSTOMER PREMISE EQUIPMENT (CPE)
     Telephone equipment, usually including wiring located within
     the customer's part of a building. ++
 

---

CUT
     To transfer a service from one facility to another. ++
 
CUT THROUGH
     The establishment of a complete path for signaling and/or
     audio communications. ++
 
DATA SET   (DS)
     A device which converts data into signals suitable for
     transmission over communications lines. ++
 
DATA TERMINAL  (DT)
     A station in a system capable of sending and/or receiving
     data signals. ++
 
DECIBEL (DB)
     A unit measurement represented as a ratio of two voltages,
     currents or powers and is used to measure transmission loss
     or gain. ++
 
DEDICATED ACCESS LINE (DAL)
     An analog special access line going from a caller's own
     equipment directly to a long distance company's switch or
     POP.  Usually provided by a local telephone company. The
     line may go through the local telco Central Office, but the
     local telco does not switch calls on this line. ++
 
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 the amplitude of the previous one is sent.
     Operates well in the presence of noise, but requires a wide
     frequency band. ++
 
DEMODULATION    (MOD)
     The process of retrieving data from a modulated signal. ++
 
DIAL LEVEL   (DL)
     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   (DP)
     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/DIAL REPEATING TIE TRUNK  (TT)
     A tie line arrangement which permits direct trunk to trunk
     connections without use of the attendant. ++
 
DIAL SELECTIVE SIGNALING   (DSS)
     A multipoint network in which the called party is selected
     by a prearranged dialing code. ++
 
DIAL TONE    (DT)
     A tone indicating that automatic switching equipment is
     ready to receive dial signals. ++
 
DIALING PLAN    (DP)
     A description of the dialing arrangements for customer use
     on a network. ++

DIRECT DISTANCE DIALING (DDD)
     A basic 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   (DOD)
     A PBX or CENTREX feature that allows a station user to gain
     direct access to an exchange network. ++
 
DROP
     The portion of outside telephone plant which extends from
     the telephone distribution cable to the subscriber's
     premises. ++
 
DRY CIRCUIT     (DC)
     A circuit which transmits voice signals and carries no
     direct current. ++
 
DUAL TONE MULTI-FREQUENCY (DTMF)
     Also known as Touch-Tone. A type of signaling which emits
     two distinct frequencies for each indicated digit. ++
 
DUPLEX
     Simultaneous two-way independent transmission. ++
 
DUPLEX SIGNALING   (DS)
     A long-range bidirectional signaling method using paths
     derived from transmission cable pairs. It is based on a
     balanced and symmetrical circuit that is identical at both
     ends. This circuit presents an E&M lead interface to
     connecting circuits. ++
 
ECHO
     A signal that has been reflected or otherwise returned with
     sufficient magnitude and delay to be perceived by the
     speaker. ++
 
ECHO RETURN LOSS (ERL)
     The loss which must be in the echo path to reduce echo to a
     tolerable amount. ++
 
ECHO SUPPRESSOR
     A device which detects speech signals transmitted in either
     direction on a four-wire circuit, and introduces loss in the
     direction of transmission. ++
 
EITHER END HOP OFF (EEHO)
     In private networks, a switch program that allows a call
     destined for an off-net location to be placed into the
     public network at either the closest switch to the
     origination or to the destination.  The choice is usually by
     time of day. Uses either Head End Hop Off or Tail End Hop
     Off. ++
 
ELECTRONIC KEY TELEPHONE SETS (EKTS)
     A generic term indicating key telephones with built-in
     microprocessors which allow access to PBX-like features as
     well as access to multiple CO lines, using 2 to 4 pair
     wiring. ++
 
ELECTRONIC SWITCH  (ESS)
     Modern programmable switch (often denoted ESS, for
     Electronic Switching System) used in most BOC telephone
     companies, many independent telephone companies, and by
     virtually all new long distance companies. Completely solid
     state electronics, as opposed to older electro-mechanical
     switches. ++
 
ELECTRONIC SWITCHING SYSTEM (ESS)
     Used as a station instrument on a PBX.  Also a Bell System
     term for electronic exchange switching equipment. ++
 
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
     PBXs. (2) An AT&T product name. (3) Used as a generic term
     for a PBX base network. ++
 
ENHANCED PRIVATE SWITCHED COMMUNICATIONS SERVICE (EPSCS)
     A private network utilizing Bell provided 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 separate signaling equipment unit. The M lead transmits
     battery or ground signals to the signaling equipment, and
     the E lead receives 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 billed for incoming calls. ++
 
EQUAL ACCESS
     Reprogramming of Local Exchange Company (LEC) switches to
     allow other long distance companies besides AT&T to be the
     "1+" primary long distance company for users of long
     distance (by creating a new type of Feature Group access
     circuit, FGD).  Also provides "10-XXX" dialing for secondary
     and casual calling, generates true hardware Answer
     Supervision when calls are terminated over FGD circuits, and
     provides ANI (Automatic Number Identification) on
     originating calls. ++
 
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 continuously occupied, e. g.
     one call per hour. ++
 
ERLANG B TABLE
     A widely used table derived from a mathematical formula
     which allows the determination of the traffic capacity of a
     given group of circuits. ++
 
EXCHANGE
     A telephone switching center. ++
 
EXCHANGE NETWORK FACILITIES FOR INTERSTATE ACCESS (ENFIA)
     AT&T's pricing arrangement for local loops offered to OCCs
     for connecting the OCC's network to the local telephone
     company's central office. ++
 
EXTENDED AREA SERVICE (EAS)
     Adding expanded local calling areas to a caller's basic
     local calling area for a (generally) small additional
     monthly fee.  The EAS local calls can be either free (after
     a small additional monthly fee is paid) or at a cost of
     reduced per call charges. ++
 
FACILITIES
     Typically refers to transmission lines or circuits, or long
     distance services. A caller's facilities are the circuits
     available to make calls. ++
 
FACSIMILE    (FAX)
     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 reproduces the original document at a distant point. ++
 
FEATURE GROUP A   (FGA)
     Line-side originating and terminating LATA access for which
     an originating subscriber dials an assigned telephone number
     that connects to a specific IC. The IC returns a tone to
     signal the caller to input additional tone-generated digits
     of the called number. ++
 
FEATURE GROUP B   (FGB)
     Trunk-side originating and terminating LATA access for which
     an originating subscriber dials a 950-WXXX number (where
     W=0,1 and XXX is the Carrier Access Code), which is
     translated to a specified XXX carrier trunk group. Optional
     rotary dial service and ANI may be available. ++
 
FEATURE GROUP C   (FGC)
     Trunk-side LATA access for AT&T, generally, on a direct
     basis between each EO and an AT&T switching system. ++
 
FEATURE GROUP D   (FGD)
     Also referred to as "Equal Access," Feature Group D is
     trunk-side LATA access affording call supervision to an IC,
     a uniform access code (10XXX), optional calling-party
     identification, recording of access-charge billing details,
     and presubscription to a customer-specified IC. ++
 
FEDERAL COMMUNICATIONS COMMISSION (FCC)
     The government agency established by the Communications Act
     of 1934 which regulates the interstate communications
     industry. ++
 
FIBER OPTICS
     High speed transmission using light to send images (in
     telecommunications:  voice or data) through a flexible
     bundle of glass fibers. ++
 
FOUR WIRE CIRCUITS
     Circuits which use two separate one-way transmission paths
     of two wires each, as opposed to regular local lines which
     usually only have two wires to carry conversations in both
     directions. One set of wires carries conversation in one
     direction, the other in the opposite direction. ++
 
FREQUENCY
     The number of complete cycles per unit of time. ++
 
FREQUENCY DIVISION MULTIPLEXING (FDM) The division of an
     available frequency range (bandwidth) into various
     subdivisions, each having enough bandwidth to carry one
     voice or data channel. ++
 
FREQUENCY RESPONSE   (FR)
     The reaction of frequencies to the circuit components. ++
 
FULL DUPLEX   (FD)
     A circuit which allows transmission of a message in both
     directions at the same time.
     Synonym:  4-wire. ++
 
FULL PERIOD   (FP)
     Relates to private line service, which is rented for the
     exclusive use of a single customer for an entire month. ++
 
FX (FOREIGN EXCHANGE) SERVICE   (FX)
     A service which allows a customer to appear to have a local
     presence in a distant part of town or, a different town
     altogether, by connecting his/her phone directly to a local
     business line in a part of town with a different exchange
     than his/her local calling area over a leased private line,
     or to a local telco in a distant town through long haul
     private lines purchased from a long distance carrier. ++
 

---

GRADE OF SERVICE   (GS)
     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. ++
 
HALF DUPLEX    (HD)
     A circuit for transmitting or receiving signals in one
     direction at a time. ++
 
HARDWIRE
     To wire or cable directly between units of equipment. ++
 
HARMONIC
     The full multiple of a base frequency. ++
 
HARMONIC DISTORTION   (HD)
     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 receiver 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 conversions
     necessary for the connection of a local loop with a long-
     haul facility. ++
 
INTERCEPT
     To stop a telephone call directed to an improper telephone
     number, and redirect that call to an operator or a
     recording. ++
 
INTERCONNECT   (IC)
     (1) The arrangement that permits the connection of
     customer's telecommunications equipment to a communications
     common carrier network. (2) The industry name for
     manufacturers, excluding the Bell system, which provide
     telephone equipment for the customer premises. ++
 
INTER-EXCHANGE MILEAGE (IXC)
     The airline mileage between two cities.
     Synonym:  Long Haul Mileage. ++
 
INTEREXCHANGE PLANT   (IP)
     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 intelligibility 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)
     Carriers providing international telecommunications
     services, including voice, telex, and data communications. ++
 
INTERSTATE
     Any connection made between two states. ++
 
INTRASTATE
     Any connection made that remains within the boundaries of a
     single state. ++
 
JITTER
     Short term instability of the amplitude and/or phase of a
     signal. Commonly called PHASE JITTER. ++
 
KEYSET
     A telephone instrument having an appearance of two or more
     telephone lines which can be accessed by depressing a button
     (key) on the face of the set. ++

KEY SYSTEM
     The equipment utilized to provide the features associated
     with key sets, including keysets, multipair cable, key
     service unit, distribution frames. ++
 
LEASED LINES   (LL)
     Any circuit or combination of circuits designated to be at
     the exclusive disposal of a given subscriber.
     Synonym:  Private line; Full Period 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); Automatic
     Route Selection; Flexible Route Selection. ++
 
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 (LATA)
     A geographic area (called "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. ++
 
LOCAL AREA NETWORK (LAN)
     Intraoffice communication system usually used to provide
     data transmission in addition to voice transmission. ++
 
LOCAL EXCHANGE CARRIER (LEC)
     A local telephone company, either one of the Bell Operating
     Companies or one of the 1400+ independent local telephone
     companies. ++
 
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. ++
 
LOOP SIGNALING
     Any of the three signaling methods which use the metallic
     loop formed by the trunk conductors and the terminating
     equipment bridges. ++
 

---

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     (PBX)
     A PBX directly connected to a tandem switch via an access
     trunk group. ++
 
MANUAL TIE LINE   (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 system. ++
 
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. ++
 
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. ++
 
MODIFIED FINAL JUDGEMENT (MFJ)
     The agreement between the U.S. Department of Justice and
     AT&T governing the breakup of the pre-Divestiture Bell
     System into AT&T and 22 Bell Operating Companies and other
     entities. On August 26, 1982, U. S. District Court Judge
     Harold Greene accepted, with modifications, an AT&T/Justice
     Department settlement terminating the government's 1974
     antitrust suit against AT&T.  Judge Greene's decree did away
     with the provisions of the 1956 consent decree that had kept
     AT&T out of competitive, unregulated ventures. ++
 
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 company's telephone
     system:  number called, length of calls, calling location. ++
 
MOST ECONOMICAL ROUTE SELECTION (MERS)
 
     Synonym:  Least Cost Routing. ++
 
MULTIPLEXING    (MP)
     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. ++
 
NETWORK
     A collection of switches connected to one another by
     transmission facilities.
 
NETWORK NUMBERING EXCHANGE (NXX)
     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. ++
 
NNX CODES
     The 3-digit code used historically for local Exchange Codes.
     "N" can be any number from 0 to 2, "X" can be any digit.
     The current numbering plan allows for more variation in
     assigning Exchange Codes, and under it Exchange Codes are
     commonly referred to as "NXXs." ++
 
NODE
     A major switching center 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)  (NANP) (AREA)
     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 "0".  Commonly referred to as "area code."  ++
 
NXX CODES  (NNX)
     The current general configuration for Exchange Codes within
     each Area Code.  See also:  "NNX Codes"  ++
 
OFFERED TRAFFIC
     The number of call attempts in any specified period of time. ++
 
OFF HOOK
     The condition which results when a telephone is lifted from
     its mounting, allowing the hookswitch to operate. ++
 
OFF-NETWORK ACCESS LINE (ONAL)
     A local exchange (Feature Group access), Foreign Exchange,
     or WATS line connecting both incoming and outgoing traffic
     from a long distance company's network to the public
     switched network.  Generally a circuit leased by a long
     distance carrier to be used by many customers not hooked
     directly into the long distance carrier's network. ++
 
OFF NETWORK CALLING
     Telephone calls through a private switching system and
     transmission network which extend to the public telephone
     system. ++
 
OFF PREMISES EXTENSION (OPX)
     An extension telephone or keyset that is geographically
     separated from its associated PBX. ++
 
ON HOOK
     The condition which results when a telephone handset is
     placed on its mounting, which causes the hook-switch to open
     its contacts. ++
 
ON NETWORK CALLING
     A term used to describe a call that originates and
     terminates on a private network. ++
 
OPERATOR ASSISTED CALLS   (OAC)  (AOS)
     Non-DDD calls requiring manual intervention. ++
 
ORIGINATING OFFICE
     The central office that serves the calling party. ++
 
OTHER COMMON CARRIER (OCC)   (AOS)
     A long distance company other than AT&T having many of its
     own long distance circuits, either owned or leased. Some
     people use OCC to refer to all AT&T long distance
     competitors, including resellers, but this is not
     technically correct. ++
 
OUT-OF-BAND
     Any frequency outside the band used for voice frequencies. ++
 
OUT-OF-BAND SIGNALING
     Use of narrow band filters to place the voice signal on a
     carrier channel below 3,400 CPS, reserving the 3,400 - 3,700
     CPS band for supervisory signals. ++
 
OVERBUILD
     Adding radio capacity to a telecommunications network. ++
 
OVERFLOW
     Switching equipment which operates when the traffic load
     exceeds the capacity of the regular equipment. ++
 

---

PAD
     A non-adjustable resistance network used to insert
     transmission loss into a circuit. ++
 
PHASE JITTER
     SEE Jitter    ++
 
POINT OF PRESENCE (POP)
     A physical location within a LATA at which an IC establishes
     itself for the purpose of obtaining LATA access and to which
     the BOC provides access services. ++
 
POINT-TO-POINT
     A communications circuit between two terminations which does
     not connect with a public telephone system. ++
 
PORT
     Entrance or access point to a computer, multiplexor device
     or network where signals may be supplied, extracted or
     observed. ++
 
POSTAL TELEPHONE AND TELEPGRAPH (PTT)
     Foreign government agencies responsible for regulating
     communications. ++
 
PRIMARY AREA
     A customer's local telphone calling area. ++
 
PRIMARY INTEREXCHANGE CARRIER (PIC)
     The IC designated by a customer to provide inter-LATA
     service automatically without requiring the customer to dial
     an access code for that carrier. ++
 
PRIMARY ROUTING POINT   (PRP)
     The switch designated as the control point for a longhaul
     telephone call. ++
 
PRIVATE BRANCH EXCHANGE (PBX)
     A private phone system (switch) used by medium and large
     companies which is connected to the public telephone network
     (local telco) and performs a variety of in-house routing and
     switching. User usually dial "9" to get outside system to
     the local lines. ++
 
PRIVATE LINE (PL)
     A full-time leased line directly connecting two points, used
     soley by purchaser. The most common form is a tie line
     connecting two pieces of a user's own phone equipment - flat
     rate billing, not usage sensitive. ++
 
PRIVATE USE NETWORK
     Two or more private line channels contracted for by a
     customer and restricted for use by that customer only. ++
 
PUBLIC SWITCHED NETWORK (PSN)
     The pre-Divestiture nationwide network maintained by AT&T
     and the independent telephone companies which provides
     nationwide, unrestricted telephone service. ++
 
PUBLIC UTILITY COMMISION (PUC)/PUBLIC SERVICE COMMISSION
(PSC)
     The state commissions regulating intrastate communications. ++
 
PULSE CODE MODULATION (PCM)
     The form of modulation in which the information signals are
     sampled at regular intervals and a series of pulses in coded
     form are transmitted representing the amplitude of the
     information signal at that time. ++
 
PULSE-LINK REPEATER
     Connects one E&M signaling circuit directly to another. ++
 
PULSE MODULATION  (PAM) (PWM) (PPM) (PCM)
     The modulation of a series of pulses which
     represents information-bearing signals.  Typical methods
     involve modifying the amplitude (PAM), width or duration
     (PWM) or position (PPM).  Pulse Code Modulation (PCM) is the
     most common modulation technique involved in telephone work. ++
 
PUSH BUTTON DIALING
 
     Synonym:  Dual Tone Multi-Frequency. ++
 
QUEUE
     A temporary delay in providing service caused by the
     inability of the system provided to handle the number of
     messages or calls attempted. ++
 
RADIO COMMON CARRIER (RCC)
     A communications common carrier that provides radio paging
     and mobile telephone services to the public. ++
 
RATE CENTER   (RC)
     A specified geographic location used by the telephone
     company to determine interchange mileage for rate
     determination purposes. ++
 
REDUNDANCY
     Duplicate equipment that is provided to minimize the effect
     of failures or equipment breakdowns. ++
 
REGENERATION
     The process of receiving distorted signal pulses and from
     them recreating new pulses at the correct repetition rate,
     pulse amplitude, and pulse width. ++
 
RE-HOMING
     A major network change which involves moving customer
     services from one switching center to another and
     establishing the necessary trunking facilities to do so. ++
 
REMOTE ACCESS  (RA)
     The ability of transmission points to gain access to a
     computer which is at a different location. ++
 
REPEATER
     An electronic device used to amplify signals which have
     become too weak. ++
 
REPEATING COIL  (RC)
     The telephone industry's term for a voice-frequency
     transformer. ++
 
RESELLER     (AOS) (OCC)
     A long distance company that purchases large amounts of
     transmission capacity or calls from other carriers and
     resells it to smaller users. ++
 
RESTORATION
     The re-establishment of service by rerouting, substitution
     of component parts, or as otherwise determined. ++
 
RETARD COIL
     A coil having a large inductance which retards sudden
     changes of the current flowing through its winding. ++
 
RINGBACK TONE   (RT}
 
     Synonym:  Audible Ringing Tone. ++
 
RINGDOWN
     A circuit or method of signaling where the incoming signal
     is actuated by alternating current over the circuit. ++
 
ROUTE DIVERSITY
     Two (or more) private line channels (circuits) furnished
     partially or entirely over two physically separate routes.
     Serves to prevent total loss of service if one cable gets
     cut or goes out. ++
 
ROUTE OPTIMIZATION
 
     Synonym:  Least Cost Routing. ++
 
ROTARY HUNT
     An arrangement which allows calls placed to seek out an idle
     circuit in a prearranged multi-circuit group and find the
     next open line to establish a through circuit. ++
 

---

SATELLITE RELAY
     An active or passive repeater in geosynchronous orbit around
     the Earth which amplifies the signal it receives before
     transmitting it back to earth. ++
 
SELECTIVE CALLING
     The ability of a transmitting station to specify by the use
     of assigned codes which of several stations is to receive a
     message. ++
 
SERVICE AND EQUIPMENT RECORD   (SAER)
     A list of equipment billed to customer by type, quantity,
     monthly charge, location and billing dates. ++
 
SF SIGNALING (SINGLE-FREQUENCY)   (SFS)
     A signaling system which uses a 2,600 Hz in-band signal on
     the voice path. The tone is on in the idle condition,
     pulsed for dialing, and off when the circuit is in use. ++
 
SHORT HAUL
     Circuits designed for use over distances of 10-200 miles. ++
 
SIGNALING
     The process of transferring information between two parts of
     a telephone network to control the establishment of
     communications between long distance carrier terminal
     points, and customer equipment required for voice grade
     dedicated circuits. ++
 
SIGNALING CONVERTER   (SC)
     A device with input and output signals that contain the same
     information but employ different electrical systems for
     transmitting that information. Used at the terminal of a
     trunk to convert the equipment signals to the system used on
     the trunk.  Examples are:  (1) ring down to SF, (2) E&M to
     SF. ++
 
SIGNALING, IN-BAND
     A type of signaling using an AC signal (usually 2,600 Hz)
     within the normal voice band. This signal can be
     transmitted from end to end of a long voice circuit without
     an intermediate signaling equipment. Since the signaling is
     audible, the signaling equipment must be arranged for "tone
     on when idle" operation. ++
 
SIGNAL TO NOISE RATIO   (SNR)
     Ratio of the signal power to the noise power in a specified
     bandwidth, usually expressed in db. ++
 
SIMPLEX (SX) SIGNALING A signaling path over a dry talking
     circuit which uses the two sides of the circuit in parallel,
     derived by connecting the midpoints of repeating coils or
     retardation coils which are across the circuit. ++
 
SINGLE SIDEBAND RADIO (SSB)
     A form of amplitude modulation of a radio signal in which
     only one of the two sidebands is transmitted. ++ Either of the
     two sidebands may be transmitted, and the carrier may be
     transmitted, reduced or suppressed. ++
 
SINGING
     A continued whistle or howl in an amplified telephone
     circuit. It occurs when the sum of the repeater gains
     exceeds the sum of the circuit losses. ++
 
SOFTWARE DEFINED NETWORK (SDN)
     A switched long distance service for very large users with
     multiple locations. Instead of putting together their own
     network, large users can get special usage rates for calls
     made on regular long distance company switched long distance
     services.
     Synonym:  Virtual Private Network. ++
 
SPECIAL GRADE NETWORK TRUNK   (SGNT)
     A trunk specially conditioned by providing amplitude and
     delay equilization for the purpose of handling special
     services such as medium-speed data (600 to 2400 BPS). ++
 
SPECIALIZED COMMON CARRIER (SCC)
 
     Synonym:  Other Common Carrier. ++
 
SPEED NUMBER
     A one, three, or four digit number that replaces a seven or
     ten digit telephone number. These numbers are programmed
     into the switch in the carrier's office or in a PBX. ++
 
STATION
     Any customer location on a network capable of sending or
     receiving messages or calls. ++
 
STATION MESSAGE DETAIL RECORDING (SMDR)
     A computer generated report showing internal usage on a
     telephone system.  Usually including extension number, trunk
     number used, phone number dialed, time of call, duration and
     operator involvement. ++
 
STORE-AND-FORWARD
     A technique in which a message is received from the
     originator and held in storage until a circuit to the
     addressee becomes available. ++
 
STORED PROGRAM CONTROL (SPC)
     A system whereby the instructions are placed in the memory
     of a commoncontrolled switching unit and to which it refers
     while processing a call for instructions regarding class
     marks, code conversions, routing, as well as for trouble
     analysis. ++
 
SUPERGROUP (SG)
     60 circuits processed as a unit in a carrier system. ++
 
SUPERMASTERGROUP (SMG)
     600 circuits processed as a unit in a carrier system. ++
 
SUPERVISION   (AS)
 
     Synonym:  Answer Supervision. ++
 
SUPERVISORY SIGNALS   (SS)  (AS)
     A signal, such as "on-hook" or "off-hook," which indicates
     whether a circuit or line is in use. ++
 
SWITCH
     Equipment used to interconnect lines and trunks. ++
 
SWITCHED ACCESS   (SA)
     Connection between caller's phone system and switch of
     chosen long distance carrier when a regular long distance
     call using regular local lines is made. Also the connection
     between the switch of caller's long distance carrier in the
     distant city and the phone being called. ++
 
SWITCH HOOK
 
     Synonym:  Hookswitch. ++
 
SWITCHING
     The operations involved in interconnecting circuits in order
     to establish communications. ++
 
SWITCHING CENTER    (SC)   (CO)
     A location at which telephone traffic, either local or toll,
     is switched or connected from one circuit or line to
     another. ++
 
SWITCHING OFFICE    (SO)  (CO)
     A telephone company office which contains a switch. ++
 
T-1(T-1)  (T1)
     24 voice channels digitized at 64,000 bps, combined into a
     single 1. ++544 Mbps digital stream (8,000 bps signaling), and
     carried over two pairs of regular copper telephone wires. ++
     Used primarily by telephone companies until 1983.  Now used
     for dedicated local access to long distance facilities,
     long-haul private lines, and for regular local service.
     Today, most any 1.544 Mbps digital stream is called T-1,
     regardless of its makeup or what the transmission medium is. ++
 
T-CARRIER    (T-1)
     A time-division, pulse-code modulation, voice carrier used
     on exchange cable to provide short-haul trunks. ++
 
TAIL END HOP OFF (TEHO)
     In a private network, a call which is carried over flat rate
     facilities (Intermachine Trunks or IMT) to the closest
     switch node to the destination of the call, and then
     connected into the public network as a local call. ++
 
TANDEM
     A switching arrangement in which the trunk from the calling
     office is connected to a trunk to the called office through
     an intermediate point. ++
 
TANDEM SWITCHING SYSTEM   (TTTN) (TSS)
 
     Synonym:  Tandem Tie Trunk Network. ++
 
TANDEM TIE TRUNK NETWORK (TTTN)
     A serving arrangement which permits sequential connection of
     tie trunks between PBX/CENTREX locations by utilizing tandem
     operation. ++
 
TANDEM TRUNKING
     Trunks which connect two or more switches together. ++
 
TARIFF
     The published rates, regulations, and descriptions governing
     the provisions of communications service. ++
 
TELCO   (BOC)
     Local telephone company. ++
 
TELECOMMUNICATIONS
     The transmission of voice and/or data through a medium by
     means of electrical impulses and includes all aspects of
     transmitting information. ++
 
TELEGRAPH   (TELEX)  (TWX) 
     A system employing the interruption of, or change in, the
     polarity of DC current signaling to convey coded
     information. ++
 
TELEPHONE
     A device which converts acoustical (sound) energy into
     electrical energy for transmission to a distant point. ++
 
TELETYPEWRITER   (TTY)  (TWX) (TELEX)
     A machine used to transmit and/or receive communications on
     printed page and/or tape. ++
 
TERMINAL
     A point at which information can enter or leave a
     communications network. ++
 
TERMINAL EQUIPMENT     (TE)
     Devices, apparatus and their associated interfaces used to
     forward information to a local customer or distant terminal. ++
 

---

TERMINATION
     (1) An item that is connected to the terminal of a circuit
     or equipment. (2) An impedance connected to the end of a
     circuit being tested. (3) The points on a switching network
     to which a trunk or line may be attached. ++
 
TIE-LINE   
     A private leased line linking two phones or phone systems
     directly.  Can ring distant phone automatically when
     telephone is lifted from its mounting, or when a short code
     is dialed. ++
 
TIME DIVISION MULTIPLEXING (TDM)
     Equipment which enables the transmitting of a number of
     signals over a single common path by transmitting them
     sequentially at different instants of time. ++
 
TOLL CALL
     Any call to a point outside the local service area. ++
 
TOLL CENTER    (TC)   (CO)
     A central office where operators (human or mechanical) are
     present to assist in completing incoming toll calls. ++
 
TOLL OFFICE   (TO)  (TC)
     A center for the switching of toll calls. ++
 
TOLL PLANT    (TP)   (TO)
     The facilities that connect toll offices throughout the
     country. ++
 
TOLL RESTRICTION    (TR)
     A restriction in outgoing trunks which counts the first
     three digits dialed and diverts calls to forbidden codes
     either to a busy tone, to the operator, or to a recorded
     announcement. ++
 
TOUCH-TONE ADAPTOR   (TT)
     A device that can be connected to a rotary dial telephone to
     allow for DTMF signaling. ++
 
TRAFFIC
     Calls being sent and received over a communications network. ++
 
TRAFFIC MEASUREMENT AND RECORDING SYSTEMS (TMRS)
     A computer generated report showing usage information of
     telephone systems. Usually this includes trunk utilization,
     outages, queueing time, and the need for additional common
     equipment. ++
 
TRAFFIC SERVICE POSITION SYSTEM (TSPS)
     A toll switchboard position configured as a push button
     console. ++
 
TRANSMISSION   (XMISSION)  (XMIT)
     The electrical transfer of a signal, message or other form
     of data from one location to another without unacceptable
     loss of information content due to attenuation, distortion,
     or noise. ++
 
TRANSMISSION LEVEL   (TL)
     The level of power of a signal, normally 1,000 Hz, which
     should be measured at a particular reference point. ++
 
TRANSMISSION SPEED   (TS)  (WPM) (BAUD)  (BPS)
     Number of pulses or bits transmitted in a given period of
     time, usually expressed as Bits Per Second (BPS) or Words
     Per Minute (WPM). ++
 
TRUNK
     A telephone circuit or path between two switches, at least
     one of which is usually a telephone company Central Office
     or switching center. Regular local CO circuits are called
     PBX trunks, because there is a switch at both ends of the
     circuit. ++
 
TRUNK GROUP    (TG)
     An arrangement of communications channels into an identical
     group. ++
 
TRUNK TYPE (TT)
     Trunks that use the same type of equipment going to the same
     terminating location. ++
 
TRUNK UTILIZATION REPORT (TUR)
     A computer printout detailing the traffic use of a trunk. ++
 
TWO-WIRE CIRCUIT  
     (1) A channel for transmitting data in one direction at a
     time. (2) A short distance channel using a single
     send/receive pathway, usually 2 copper wires, connecting a
     telephone to a switch. ++
 
TELETYPEWRITER EXCHANGE SERVICE (TWX)  (TELEX)  (TTY)
     A service whereby a customer's leased teletypewriter is
     connected to a "TWX" switchboard and from there connected
     over regular toll circuits to a teletypewriter of any U.S.
     customer who subscribes to a similar service. ++

UNIFORM CALL DISTRIBUTOR (UCD)   (ACD)
     A device located at the telephone office or in a PABX which
     distributes incoming calls evenly among individuals. ++
 
UNIFORM SERVICE ORDER CODE (USOC)
     The information in coded form for billing purposes by the
     local telephone company pertaining to information on service
     orders and service equipment records. ++
 
VALUE-ADDED NETWORK SERVICE (VANS)
     A data transmission network which routes messages according
     to available paths, assures that the message will be
     received as it was sent, provides for user security, high
     speed transmission and conferencing among terminals. ++
 
VIA NET LOSS (VNL)
     The lowest loss in dB at which a trunk facility can be
     operated considering limitations of echo, crosstalk, noise
     and singing. ++
 
VOICE CONNECTING ARRANGEMENT    (VCA)
     An interface arrangement provided by the telephone company
     to accomodate the connections of non-carrier provided voice
     terminal equipment to the public switched telephone network. ++
 
VOICE FREQUENCY (VF)
     Any of the frequencies in the band 300-3,400 Hz which must
     be transmitted to reproduce the voice with reasonable
     fidelity. ++
 
VOICE GRADE   (VG)
     An access line suitable for voice, low-speed data,
     facsimile, or telegraph service. Generally, it has a
     frequency range of about 300-3000 Hz. ++
 
VOICE GRADE FACILITY (VGF)
     A circuit designed to DDD network standards which is
     suitable for voice, low-speed data, facsimile, or telegraph
     service. ++
 
WIDE AREA TELECOMMUNICATIONS SERVICE (WATS)
     WATS permits customers to make (OUTWATS) or receive
     (INWATS) long-distance calls and to have them billed on
     a bulk rather than individual call basis. The service
     is provided within selected service areas, or bands,
     by means of special private access lines connected to
     the pubic telephone network via WATS-equipped central
     offices. A single access line permits inward or outward
     service, but not both. ++
 
WIDEBAND   (WB)
     A term applied to facilities or circuits where bandwidths
     are greater than that required for one voice channel. ++
 
WIRE CENTER   (WC)
     The physical structure that houses one or more central
     office switching systems. ++
 
"0" or "0-"   (AOS)
     Zero minus dialing. Allows a caller to dial zero and
     nothing else to get the Operator. ++
 
"0+"    (AOS)
     Zero plus dialing. An operator assisted long distance call
     which is charged to the calling party. ++
 
"00+" or "00-"   (OCC)  (AOS)
     Double zero dialing. Allows a caller to get an AT&T
     Operator in areas in which dialing only one zero would
     connect the caller with the local Operator because AT&T has
     given Operators back to the local telephone company. ++
 
"1+" DIALING   (IXC) (OCC)  (AOS)
     The capability to dial "1" plus the long distance number for
     calls withing the North American Numbering Plan area.
     Intra-LATA calls are carried by the local telephone company.
     Inter-LATA calls are carried by the caller's primary
     carrier, or by AT&T if equal access has not come to the
     caller's area yet. ++
 
"10-XXX" DIALING   (OCC) (AOS) (IXC)
     The ability to send calls over a carrier other than a
     caller's primary carrier by dialing "10-XXX" then "1+" the
     long distance number, where "XXX" is the 3-digit Carrier
     Code of the alternative long distance company (also called a
     secondary carrier). Available only to Equal Access
     customers.  ++
 
800 SERVICE   (800)
     The ability of a caller to dial a long distance telephone
     number without incurring a charge for the call, which is
     paid for by the party offering the 800 number.
     Synonym:  Inward WATS service. ++
 
900 SERVICE   (900) (976)
     Allows callers to receive information from the service
     provider via a recorded audio message, which can range from
     60 seconds to a continuous live hookup, by calling a 900
     number. This service can also be used to enable callers to
     vote or "make a choice" by dialing one of two 900 numbers.
     900 calls are typically billed to the caller at much
     higher rates than regular calls. ++
 
976 NUMBERS   (900)  (976)
     Service which allows callers to listen to recorded messages
     such as horoscopes, 'adult' dialogue, stock market or sports
     reports by calling 976-xxxx. The local telephone company
     charges callers a fee which is split between the local
     telephone company and the service provider. ++