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Online Telecom Library - Terms & Acronyms
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| K | L | M
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| R | S | T
| U | V | W
A
AC/DC RINGING
A method of telephone signaling that uses alternating
current to operate a ringer and direct current to actuate a relay
which stops the ringing when the called party answers.
ACTIVATION CODE
Many long distance dial around plans will have a 5 or
6 digit activation code that must be used on your very first call
(on your first call only). This activation code is used to know
who it was that referred you to that phone calling plan. The use
of an activation code does not affect your phone in any way and
does not switch your long distance carrier.
ALTERNATE ROUTE
A second or subsequent choice path between two points, usually
consisting of two or more trunk groups in tandem. This term (or
alternate routing) is also used as a verb to define the act of
selecting an alternate route.
AMBIENT NOISE
Background noise existing in any environment, unrelated to noise
induced in the transmission medium.
AMPLIFIER
Any device that, by enabling a relatively low level received signal
to control a local source of power, delivers an amplified reproduction
of the received signal.
AMPLITUDE
The size of magnitude of a voltage or current signal.
ANALOG
Signals which make use of electrical or physical analogies
(i.e., varying voltages, frequencies, distance, etc.) to produce
a signal of a continuous (rather than of a pulse or digital) nature.
ANALOG CHANNEL
A channel capable of transmitting analog signals within the specified
bandwidth of the facility. Voice channels are analog channels.
ANALOG SIGNAL
A signal that varies in a continuous manner, such as voice or
music. An analog signal may be contrasted with a digital signal
that represents only discrete states. The signal put out by a
data set has both analog and discrete characteristics.
AREA CODE
A three-digit number identifying one of the assigned geographic
areas in the North American direct assistance dialing numbering
plan.
AREA EXCHANGE (also see Exchange)
Geopolitical areas set up for the administration of local telephone
service. Usually a single metropolitan area or collection of towns
and villages sharing a common area of community interest.
ASCII
An acronym for American Standard Code for Information Interchange,
an 8-level alphanumeric code (7 bits + parity bit).
ATTEMPT
A call offered to a telecommunications system, whether or not
it is completed.
ATTENUATION
The difference between transmitted and received power due to loss
through equipment, lines, or other transmission devices. Usually
measured in decibels.
B
BACK-HAUL
A communications path which takes traffic farther than the ultimate
destination, then routes it back. This is done because the cost
of transmission to the more remote location is much lower than
a more direct route.
BILLING INCREMENTS
The length of your call which relates to what your per
minute rate is, be it based on one minute billing increments,
6 second increments, etc. If you have one minute billing increments,
a 12 second call will be rounded up to the full minute.
BACKBONE
That portion of a communications network connecting primary nodes
via multiplexing techniques; a primary shared telecommunications
pathway by which multiple users are served via multiplexing at
designed jumping-off points.
BACKGROUND NOISE
Random signals that can be attributed to the unpredictable movement
of free elections in a telephone channel. (See AMBIENT NOISE.)
BIDIRECTIONAL SWITCH
Any switch in which a moving contact level travels in two directions
to connect to a desired fixed contact. While the most common combination
is a vertical motion followed by an angular motion, other combinations
are possible.
BINARY
Pertaining to the property which permits the selection of two
distinct possibilities. A binary code makes use of two distinct
characters (i.e., "0" and "1," positive and
negative pulses). The flow of this information is referred to
as a binary stream or binary code.
BINARY SWITCH
A switch that must exist in one of only two states: on/off, zero/one,
etc.
BIT
A contraction of binary digit, the smallest unit of coded information.
Data bits are used in combination to form characters, framing
markers, parity, transmission synchronization, and so on.
BIT RATE
The speed at which bits are transmitted. Expressed as bits per
second or bps.
BIT STREAM
Any reference to a binary signal stream without regard to a code.
BPS (BITS PER SECOND)
A measure of speed in serial transmission - generally the number
of signaling elements per second; synchronous with baud. Bps is
also used to describe hardware transmission capabilities, as in
a 1200 bps modem.
BLOCKED ATTEMPT
An attempt that cannot be further advanced toward its destination
due to an equipment shortage or failure in the network.
BLOCKING
The inability of the calling party to be connected to the called
party be cause either:
1. All permitted trunk paths are busy.
2. A path between a given inlet and any permitted free outlet
of the
switching network of a switching system is unavailable.
BRIDGING
The technique whereby additional stations may be served from a
2-point facility by extending the facility from a "bridge"
at one of the terminating points of the facility.
BROADBAND
A communication channel having a bandwidth greater than a voice
grade channel and, therefore, capable of higher speed data transmission.
BUSY
The condition of a line resulting in the inability to complete
a call be cause it is in use or in trouble.
BYPASS
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.
BYTE
A group of binary digits which are processed as a unit by a computer
or telecommunication equipment.
C
CARRIED TRAFFIC
That part of the traffic offered to a group of servers that successfully
seizes a server, i.e., carried traffic equals offered traffic
minus overflow traffic.
CARRIER
A company authorized by the appropriate regulatory agency to pro
vide communications services. (Also see COMMON
CARRIER).
Carrier Identification Code (CIC)
A long distance company's one-of-a-kind code, mainly
used so the local phone provider knows who your long distance
carrier is. Also known as a PIC Code.
CARRIER ACCESS CODE
A set of digits dialed by an end user in addition to, or in lieu
of, a destination code to designate the IC to be used for that
particular call. Various formats are or will be available for
access to Message Telecommunication Service/Wide Area Telecommunications
Service (MTS/WATS)-like services. These include a digit number
(lOXXX - dialed as a prefix to the destination code) or a 7-digit
number (950-lOXX), where XX is used in both cases to identify
a particular IC. Feature Group A arrangements will continue to
use the BOC locally assigned NPA ~ 7 digits as a carrier access
code.
CCITT
An international telecommunications advisory committee
- "Committee Consultant International Telegraphique et Telephonique"
- established by the United Nations (as a subgroup within the
International Telecommunications Union) to recommend worldwide
standards for communications common carrier services.
CCS (See Completed Call Seconds)
CHANNEL
The smallest subdivision of a circuit in which a single type of
communication service is provided (i.e., voice channel, data channel).
CHANNEL BUSY TONE
An audible signal indicating a call cannot be completed because
all switching paths or toll trunks are busy, or that equipment
is blocked. The tone is applied 120 times per minute.
CIC (See Carrier Identification Code)
CIRCUIT
1. A communication path between two or more points.
2. A network of circuit elements, such as resistors, inductors,
capacitors,
semiconductors, etc., that perform a specific function.
3. A closed path through which current can flow.
CIRCUIT SWITCHING
A switching system that completes a dedicated transmission path
from sender to receiver at the time of transmission. The connecting
of two or more channels to create a through circuit between two
points.
CLASS OF SERVICE
One of several categories of main stations provided in the tariff
for the purpose of charging customers for the particular service
selected. Different routing treatments may be required for individual
categories. The following are some common examples of services
that are frequently offered:
- Coin
- Flat Rate
- 800-Service
- Message Rate
- PBX
- WATS
CLEC (Competitive Local Exchange Carrier)
A phone company that competes with an (ILEC) Incumbent
Local Exchange Carrier, yet a CLEC can use the infrastructure
of an ILEC.
COMMON CARRIER
A government-regulated private company that furnishes the general
public with telecommunications service and facilities; e.g., a
telephone or telegraph company.
COMSAT (COMMUNICATIONS SATELLITE CORPORATION)
Created by authorization of Congress in the Communications Satellite
Act of 1962. This private corporation (not an agency of the United
States Government, although subject to governmental regulation)
was created primarily to provide for the establishment, operation,
and management of a commercial communications satellite system.
COMSAT presently acts as manager for INTELSAT and also represents
the United States in INTELSAT.
COMPLETED CALL SECONDS (CCS)
A unit of traffic quantity used in traffic engineering. One CCS
is the equivalent of a 100-second call or an aggregate of 100
call-seconds.
COMPRESSION
The switching function of making a large number of inputs all
accessible to a smaller number of outputs. The inverse is EXPANSION.
Country Code (See Destination Code)
CROSS CONNECTIONS
Flexible, interchangeable connections usually made on a distribution
frame to associate two pieces of equipment, two cable pairs, or
one of each.
CYCLE
- The interval of space or time necessary
to complete one set of events before they are repeated.
- The amount of time necessary to complete one waveform.
D
DATA
Information which is arranged in a formalized manner suitable
for further handling. Usually this implies automatic handling
such as communications or processing.
DATA COMPRESSION
The process of reducing the volume of transmitted data while conveying
the original information content.
DATA LINK
The communications path between a pair of data communications
de vices. The data link includes all devices and transmission
media in the path.
DEDICATED LINE / SERVICE
A communication line or system provided to a single organization
and used exclusively by that organization.
DEMODULATION
The process of converting information signals previously modulated
into transmission carrier form back into the form in which they
existed before the modulation process.
DESTINATION CODE (Also Country Code)
A combination of digits that provides a complete address to reach
a destination in the message network. Most destination codes are
made up of some of the following components:
DIAL TONE DELAY
A measure of time required to provide dial tone to customers.
This measures one aspect of the performance of a switching system.
DIGITAL MICROWAVE
A microwave system in which most or all of the modulation of the
radio frequency carrier is controlled directly by digital signals.
The carrier is still a radio frequency and the modulation may
be frequency or phase shift, but the control of that modulation
is the digital bit stream. This is in contrast to analog microwave,
in which a digital bit stream would be converted to an analog
carrier by a voice grade modem and then frequency shifted up to
the appropriate carrier frequency.
DIGITAL TRANSMISSION
The transmission of a digital signal between two or more
points. The usual definition applies to the manner in which the
transmission carrier is modified to carry the transmitted information.
For example, in digital microwave systems, the radio frequency
carrier is an analog signal, but its information modulation is
derived from the digital signal.
DIRECTORY ASSISTANCE (DA)
A service in which a customer will be connected to an operator
at a DA bureau by dialing the proper service code or number and
shall be told the directory number of the customer whom he/she
desired to call, provided that the customer's number is, or will
be, published (listed) in the telephone directory. (Formerly called
information service.)
E
EARTH STATION
The end of a satellite communications link which is located on
earth. It may be a transmit/receive station or it may be a receive-only
station.
ECHO
The distortion created when a transmitted signal is reflected
back to the originating station. It becomes a serious distraction
to a speaker when the echo signal is delayed in time.
ECHO CANCELLER
A device used in a transmission line to reduce echo; it operates
by put ting a signal on the return transmission path which is
equal and opposite to the echo signal.
ECHO SUPPRESSOR
A device used in a transmission line to reduce echo; it operates
by attenuating the return signal path from the distant end.
END USERS
Customers who use (rather than provide) telecommunications services,
i.e., those who either originate or terminate telecommunications.
ENHANCED SERVICES
As defined in Computer Inquiry II, an enhanced service is any
offering over the telecommunications network that is more than
a basic service, e.g., services that use computer processing applications
to act on the format, content, code, protocol, or other aspects
of the end user's transmitted information. They provide the end
user with additional, different, or restructured information and
may involve end user's interaction with stored information. (See
BASIC SERVICES.)
EXCHANGE OR EXCHANGE AREA
A geographic area established by a BOC for the administration
and pricing of telecommunications services in a specified area
that usually em braces a city, town, or village and its environs.
It consists of one or more central offices and the associated
facilities used in furnishing telecommunications service within
that area, and does not have the same meaning as the exchanges
defined by the MFJ. [See LOCAL ACCESS AND TRANSPORT AREA (LATA).]
EXCHANGE SERVICE
A communication service permitting the interconnection of any
two of a number of customers' telephones through switching equipment.
EXTENDED AREA SERVICE
A telephone service which provides service beyond the usual boundary
to contiguous areas without toll charges. This exists in areas
where there is a community of interest. The toll charges are not
applied in return for a somewhat higher basic exchange service
rate.
F
FACILITIES NETWORK
The aggregate of transmission systems, switching systems, and
station equipment; it supports a large number of traffic networks.
FACILITY
Any one or all of the elements of a physical plant used
to provide communications services. Often used synonymously with
a transmission path including all of the physical equipment associated
with that path.
FEDERAL COMMUNICATIONS COMMISSION (FCC)
The federal agency empowered by law to regulate all interstate
and foreign radio and wire communications services originating
in the United States, including radio, television, facsimile,
telegraph and telephone systems. The agency was established under
the Communications Act of 1934. Current legislation to rewrite
the 1934 Act proposes changing the FCC's authority regarding regulation
jurisdiction from interstate service to interexchange services
which would include both interstate and much of what is, today,
intrastate toll services.
Fiber Optics
Technology based on thin filaments of glass or other
transparent materials used as a method for transmitting coded
light pulses that represent data, images, or sound.
FRAME
A segment of a signal, analog or digital, that has repetitive
characteristics in that corresponding elements of successive frames
represent the same things. Examples are: a television frame, which
represents a complete scan of a picture; or a telemetry frame,
which represents values of a number of parameters in a specific
order. In a time division multiplexed system, a frame is a sequence
of time slots, each containing a sample from one of the channels
served by the multiplexer system, and each channel occupies the
same sequence position
in successive frames.
FRAMING
The process of establishing a reference so that time slots or
elements within the frame can be identified.
FREQUENCY
The rate of recurrence of some repetitive event such as an electrical
signal. It is measured in cycles per second (cps) or Hertz.
FREQUENCY MODULATION (FM)
A modulation technique in which the carrier frequency
is shifted by an amount proportional to the value of the modulating
signal. The amplitude of the carrier signal remains constant.
G
GIGABIT
A gigabit is equal to one billion bits.
GIGAHERTZ
One billion cycles per second.
H
HARDWIRED
- Equipment which is wired together so that its function is
fixed (as
compared to equipment in which plug-in components may be varied
to change the function).
- Equipment units which are permanently cabled together (as
compared
to those which may be flexibly interconnected at a distributing
frame).
HERTZ (HZ)
A unit of frequency. One Hertz is equal to one cycle
per second.
I
IEC (Interexchange Carrier)
The carrier that provides long distance service between the Local
Exchange Carrier (LEC) and the Local Access Transport Area (LATA).
INTERLATA
A term used to describe services, revenues, functions,
etc. that relate to telecommunications originating in one LATA
and terminating in another LATA or outside of a LATA.
INTERLATA CARRIER (IC)
Any carrier that provides telecommunications services
between a point in a LATA and a point in another LATA or outside
a LATA.
INTERTANDEM TRUNK GROUPS
A category of trunk groups that interconnect tandems.
INTRALATA
A term used to describe services, revenues, functions, etc. that
relate to telecommunications originating and terminating within
a single LATA.
INTRASTATE
Within a given state. Communications services within a state are
generally regulated by the state utility commission.
K
KILOBIT
One thousand bits. It is usually used to designate 2 to the 10th
bits, which is actually 1024 bits. One or more characters or words
which are used to identify a record, message or file in an information
handling system.
KILOHERTZ
One thousand hertz, or one thousand cycles per second.
L
LEC (Local Exchange Carrier)
tHE local phone service provider.
LINE
- A pair of wires carrying direct current
between a central office and a customer's terminal. A line is
the most common type of loop. (See LOOP.)
- In carrier systems, the portion of a
transmission system that extends between two terminal locations.
The line includes the transmission media and associated line
repeaters.
- Also used to indicate the side of a
piece of central office equipment that connects to or toward the
outside plant; the other side of the equipment is called drop
side.
- A family of equipment or apparatus designed to provide a
variety of styles, a range of sizes, or a choice of service
features.
LOA (Letter of Agency)
A form that the customer signs that gives permission for a switch
of the customers long distance service.
M
Ma Bell
Reference to AT&T.
MAC
The protocol that determines the transmission of information
on a local area network. The MAC is referred to as the sublayer
of the data link layer which is a part of the open systems interconnect
model.
MAC Address
A data link layer identifier that is placed into every
port/device that connects to a LAN. MAC Addresses are also referred
to as hardware addresses or physical addresses.
MAIN PBX
The initial PBX that interfaces with the public telephone
network via central office trunk lines.
MEGABIT
One million bits.
MEGABYTE
One million bytes, or 1,000 kilobytes.
MEGAHERTZ
One million hertz.
MICROWAVE
A wireless technology that uses the high frequency band
of the radio spectrum to transmit analog and digital information.
Microwave systems can have bandwidths up to 300 times greater
than broadcast TV networks and several times greater than cable
TV networks.
MINIMUM USAGE CHARGE
If you see a calling plan where you would pay a small fee if your
monthly long distance usage is under a certain amount, this is
a minimum usage charge. A minimum usage charge differs from a
monthly fee.
N
NARROWBAND
An older cable TV system with limited channel capacity.
NATIONAL ACCESS FEES
A Federal tax placed upon telecommunication services
provided by telephone companies.
NETWORK SERVICE PROVIDER
A company which provides telecommunication services with
their own or leased equipment.
O
ONE-WAY TRUNK
A trunk circuit which can be seized at only one end.
OPERATOR NUMBER IDENTIFICATION (ONI)
Operator identification of a calling number is required
because there is no ANI equipment in the originating office. The
operator obtains the calling station number then keys this number
into CAMA equipment.
ORDER VERIFICATION PROCEDURE (Also Third Party
Verification)
One of the things that long distance carriers will do to cut down
on fraud is ask you to verify the order you placed when you requested
long distance service. Some carriers might require an actual signature
from you, but others will allow you to sign up online or over
the phone, then you must follow their procedure to verify that
you want their long distance service. The procedure varies between
carriers, but usually you will either have to call a toll free
number to verify, send an email to verify, or in some cases the
carrier will contact you to verify your order. If you are asked
to call a toll free number to verify, you must call from the same
phone number that you are requesting long distance service on.
P
PACKET
A group of bits treated as a unit for communications routing.
This unit includes addressing, routing, and customer data.
PACKET SWITCHING
A switching technique where addressed packets are individually
routed to the destination. The routing is a function of the availability
of transmission paths. Long messages are broken into multiple
packets which are routed individually and then reassembled in
the proper order at the destination.
PAYPHONE SURCHARGE
This is a Federally mandated fee that a long distance company
must pay to the payphone company when a call is made using a calling
card or when a call is made to a toll free number. This fee varies
between carriers but is usually 35 or 40 cents.
PBX (SEE Private Branch Exchange)
PIC (See Primary Interlata Carrier)
PICC (See Presubscribed Interexchange
Carrier Charge)
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. POPs apply to both switched and special
access, al though different ones may be used for different services.
POINT-TO-POINT
A line or a transmission between two points which neither requires
nor transmits an intermediate point.
PRESUBSCRIBED INTEREXCHANGE
CARRIER CHARGE (PICC)
This is a Federally mandated charge that every long distance carrier
must pay to the local phone company on any business that has 2
or more business lines. You should never pay a PICC on a residential
line, no matter how many lines you have. The PICC varies between
long distance carriers.
PRIMARY INTERLATA CARRIER (PIC)
The IC designated by a customer to provide interLATA
services automatically without requiring the customer to dial
an access code for that carrier. (See PRESUBSCRIPTION.)
PRIVATE BRANCH EXCHANGE (PBX)
A private telephone switching system, usually located on a customer's
premises. The abbreviation PBX is a general term applied to all
types of PBXs, both manual and automatic. The abbreviation PABX
implies an automatic PBX. The system provides intra-premises exchange
telephone service, as well as access to the public exchange network
and/or private facilities. Although these switches are increasingly
being used for data communications, as well as voice, they are
primarily designed for voice.
PROTOCOL
A set of rules by which a communication network is operated
in order to perform a specified set of communications functions.
Binary synchronous communications is a data communications protocol.
PUBLIC SWITCHED NETWORK
Any common carrier network that provides circuit switching
between public users. The term is usually applied to the public
telephone net work, but it could be applied more generally to
other switched networks such as Telex, Execunet, etc.
PUBLIC SWITCHED TELEPHONE NETWORK (PSTN)
The network is an integrated system of transmission and
switching systems, signaling processors, and associated operations
support systems (OSS) that is shared by the public. Sometimes
referred to as PTN, PSN, PN (Public Telephone Network, Public
Switched Network, Public Network.)
PUBLIC TELEPHONE SERVICE (PTS)
Ordinary telephone service in which a customer has a connection
to a central office and can be connected to any other customer
of the service. Sometimes called plain old telephone service (POTS).
R
REDUNDANCY
Additional system or information elements used to improve
reliability. System components would include back-up devices such
as stand-by processors or modems. Information redundancy includes
parity bits and the extra bits used in error checking codes.
RELAY
- A device, usually electromechanical, by
which the variation in current in one circuit causes the opening
or closing of contacts controlling the current flow in one or
more other circuits.
- A process of retransmitting signals or messages through an
intermediate point or repeater.
REMOTE ACCESS
A process of communicating with a computer from a location
which is physically removed from that computer.
REROUTING
A short-term change in the routing of selected traffic
items. Rerouting may be planned and recurring or a reaction to
a nonrecurring situation. It is generally associated with network
management activity.
ROUTING
The assignment of a communication path through a network
with multiple possible paths in order to connect an originating
station with the requested destination station.
S
SATELLITE COMMUNICATION
- An earth orbiting system which receives
radio signals from ground based antennae (earth stations) and
retransmits these signals, at a slightly different frequency,
back to other earth stations.
- A secondary system, operating remotely from, but in conjunction
with, a central control system.
SIGNALING SYSTEM 7 (SS7)
The most advanced signaling system (replacing CCIS6)
being implemented in telco networks. SS7 allows customers to access
databases through the Common Channel Signaling network and utilize
such services as CLASS, BOC-800, and other future services.
SWITCH
A mechanized operations system that inventories and assigns
nodal equipment and related facilities. SWITCH is designed to
replace COS MOS.
SWITCHING
The process of interconnecting circuits to form a communication
path between pairs of stations out of a population of a much larger
number of potential stations. The process may be implemented using
a wide range of technologies and it includes a number of peripheral
functions in addition to the connection function such as call
supervision, routing, call recording, etc.
T
T-1
A dedicated line which has 24 channels that can carry both voice
and data transmission. Each channel supports 64Kbits per second.
If a business needs a dedicated line but only needs to lease,
for example, 15 lines, this is called a Fractional T1.
TANDEM
The connection of networks or circuits in series; that
is, the connection of the output of one circuit to the input of
another.
TANDEM SWITCHING SYSTEM
A switching system in the message network that establishes
trunk-to trunk connections.
TANDEM TRUNK
A trunk circuit which connects a tandem switch to another
tandem switch or to a telephone company central office.
TELECOMMUNICATIONS
- The transmission of intelligence through
a medium by means of electrical impulses.
- The collective services of the communications common carrier.
TELEPHONY
A general term encompassing all the technology associated
with voice telecommunications.
TERMINATION
- An item that is connected to the
terminals of a circuit or equipment.
- An impedance connected to the end of a
circuit being tested.
- The points on a switching network to which a trunk or a line
may be attached.
TIME DIVISION MULTIPLEXING (TDM)
A transmission technique in which a single communications channel
is subdivided into a number of time slots, each of which carries
the information of a separate data stream.
TIME OUT
The process of exceeding a preset time limit within which
some specified action is to have taken place. For example, if
a station fails to respond to a poll within a set time, it is
said to have timed out.
TOLL CALL
Any call, subject to charge, to a destination outside
of the local service area of the calling station. Also referred
to as a long distance call.
TRAFFIC
A flow of attempts, calls, and messages.
TRAFFIC CAPACITY
The total volume of traffic which a communications facility
can handle within a specified time period.
TRAFFIC USAGE
Total occupancy of a network. This is calculated as the product
of holding time and calling rate, and can be expressed as call-hours.
Traffic usage may be made up of many short calls or a few long
calls - it doesn't matter.
TRUNK
In a network, a communications path connecting two switching
systems used in the establishment of an end-to-end connection.
In selected applications, it may have both of its terminations
in the same switching sys tem.
TRUNK CIRCUIT
A circuit, part of a switching system, associated with
the connection of a trunk to the switching system. It serves to
convert between the signal formats used internally in the switching
system and those used in the transmission circuit, and it performs
logic and sometimes memory functions associated with supervision.
TRUNK GROUP
The output side of the switching network in the Number
5 Crossbar System.
U
UNINTERRUPTIBLE POWER SUPPLY (UPS)
A battery back-up system used when power goes out. It
converts DC battery power to AC power to run the system.
UPLINK
The transmission link from an earth station to a communications
satellite.
USAGE
A measurement of the load carried by a server or group
of servers, usually expressed in CCS. Usage may also be expressed
in erlangs.
V
VOICE FREQUENCY (VF)
The frequency range for the average human voice, which,
when applied to station carrier, is 300 to 3400 Hz.
WIDE AREA NETWORK (WAN)
A communications network, serving geographically separate
areas. Can be established by linking two or more metropolitan
area networks (MANs) together to allow data terminals in one city
to access data in another city, county, or state.
