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TRANSCRIPT
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Chapter 1
Introduction toTelecommunications
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Objectives
Be able to explain what telecommunications
is.
Have a basic understanding of the variousnetworks used to transmit voice, video, and
data signals from one location to another.
Know the types of media used to convey
telecommunications signals between asender and a receiver.
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Objectives (continued)
Understand the basics of the three majorvoice communication technologies(keysystem, private branch exchange, and
automatic call distributor) available to abusiness enterprise and the type of businessbest served by each of these technologies.
Have a basic understanding of personalcomputer-based voice communicationsystems, referred to as computer telephonyintegrated (CTI) systems.
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Objectives (continued)
Have a basic understanding of what a local
area network and a wide area network are
and how a business uses them to meet data
communication needs.
Have a basic understanding of Hypertext
Markup Language (HTML) and web
browsers.
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Telecommunications
Communication over a distance
Voice
Video
Data
Telecommunications voice communications
Data Communication data signals
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Telephone Connected to
Central Office
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Public Switched Telephone
Network (PSTN)
Voice signals emerge from telephone asanalog (analogous) signals
All telephones connected to a local central
office Automated switching system connects callers to
desired location
Contains a line circuit for each telephone
connected to it Codec (coder/decoder) converts analog signals
into digital signals
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Packet (or Public) Data
Network
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Packet Data Network (PDN)
Digital data can be transmitted over the
PSTN
Modems
Packet Data Network
Wide area network
Uses PSTN facilities reserved for data
transmission
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Beginning of
Telecommunications
Samuel F.B. Morse (1791-1872)
Guglielmo Marconi (1874-1937)
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Telegraph (Morse)
Morse formed a telegraph company based on
his invention in 1845.
Western Union Telegraph Company was
established in 1856.
Morse developed
The repeater, that could regenerate electrical
signals.
Morse code, to transmit letters of the alphabet.
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Radio (Marconi)
Marconi discovered how to make electric
energy radiate from wire into air
(electromagnetic radiation).
Radio waves first used for wireless telegraph.
Not long before voice signals were being
carried.
In the 1940s radio signals were used to
transmit video and television was born.
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Fiber Optic Technology
Two scientific developments in the 1980s
A way transmit voice, data, and video using light.
A way to transmit light signals over narrow
ribbons of glass (glass fiber).
Sprint built an entire network using fiber
Completely new network (not stuck with old
technology). First Interexchange Carrier (IEX) with an all-digital
network for long distance calls.
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Invention of the Telephone
In 1876, Elisha Gray and Alexander Graham
Bell filed papers with the patent office for an
invention called the telephone.
Gray filed a disclosure notification.
Bells father-in-law filed a patent for Bell.
The Supreme Court ruled in a split decision
that Bell is to be recognized as the inventor ofthe telephone.
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Relay Centers and Speed of
Delivery
The telegraph system
The telephone system
Local Exchange Carriers (LECs) Interactive-Voice-Response (IVR) systems
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Connection of Telephone
Offices
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Connection of Telephone
Offices
Telegraph system
Far superior to U.S. mail system
Sender still had to wait hours for response due to
delay involved in messenger locating recipient
Telephone company in 1870s originally used
same approach
Customer would give operator a message alongwith recipient
Message would be relayed to telephone center in
next town
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Long Distance Network
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Long Distance Network
Toll network
Established by Bell Company
Reduced number of relays made to complete long
distance calls Managed by AT&T Long Lines department
Local Exchange Carrier (LEC) Bell and non-Bell
Connected to an AT&T toll center
Could take up to an hour to get call through
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Function Automation
First functions to be automated were localoperator functions
Next were long distance operator functions
Interactive-Voice-Response (IVR) systems Collect calls
Person-to-person
Allow caller to provide information via scriptedquestions
Operators used to handle calls rejected byautomated system
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Another Type of Relay Center
Hearing impaired
Operators at relay centers are called agents
Operator talks to hearing party
Operator uses teletype to communicate with
hearing impaired party
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Relay Center
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Telecommunications for the
Hearing Impaired
Major telecommunications service
Each state government contracts to provide
service via relay centers
Relay agent communicates with hearing party
Hearing impaired party uses a teletype
Uses a special purpose modem
Different code than a PC for transmission
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Increasing Speed of
Telecommunications
Significant increases in speed in which
telephone call can be made
Automating the switching systems
Eliminating the need for operators to make
connections
Development of computer-controlled
switching systems Development of signaling systems to connect
computer-controlled switching systems
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SS7 Network
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Signaling System 7 (SS7)
Contains special purpose computers and databases
connected in a data network
Connects all computer-controlled switching systems
Provides a path that allows information from onecomputer-controlled switching system to reach
another
Caller ID
Call forwarding
Conference calling
Establishes calls in a few milliseconds
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Increasing Ability to Handle
Data
PSTN has evolved into an all-digital network
Very Large Scale Integrated Circuit (VLSI)
chips
Large number of components
Small in size and cost
Fiber optic cables for transmission media
Multiplexing placing many signals over one
transmission medium
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Multiplexer
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Multiplexer
Very Large-Scale Integrated Circuit (VLSI)chips
Hardware devices that handle digital signals
Small (in size and cost), special purposeintegrated circuit chips
Use of fiber optic cables for transmissionmedia has helped make enormously fast
signal changes possible Multiplexing is a technique used to place
many signals over one transmission medium
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Multiplexing Using DWDM and
OC-48
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Dense Wave Division
Multiplexer (DWDM)
Uses 32 different light waves to carry signals
over one fiber
Each multiplexer sends signals at 10 billion
signal changes per second
One fiber can carry 320 billion signal changes
per second
One fiber cable can contain 140 fibers for 22
trillion signal changes per second
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Fiber Cable Networks
Handle all types of telecommunications services
Telephone calls
Data and video
Internet Business users
Link personal computers, file servers, and mainframes
Cellular technology
Connnect to switching centers
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Fiber Carrying All Types of
Circuits
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Telecommunications for Voice
Applications in Business
Large businesses have a telecommunications
department to handle use of technology
Voice and data services have merged
Voice-Over Internet Protocol (VoIP)
Private switching systems
Private Branch Exchange (PBX)
Keysystem
Automatic Call Distributor (ACD)
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Voice-Over Internet Protocol
(VoIP)
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Voice-Over Internet Protocol
Delivers voice and data over the data
network
Standards developed
Quality improved
Can replace analog telephones
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PBX Switching System
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PBX Switching System
Has all telephones of the business connected
to it
Also connected to the local exchange carrier
(Central Office, CO lines)
Employees can dial each other directly or dial
9 for a CO (outside) line
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PC-Based PBX or UnPBX
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UnPBX
Furnished via personal computers
Special cards containing RJ-11 jacks
Jacks allow for connecting to telephones or C.O.
lines
Can also provide information about the call
on its screen
Computer Telephony Integrated (CTI)systems do this automatically using caller ID
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Keysystems
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Keysystems
Many small businesses do not need a PBX
Used when business has
Less than 24 telephones
Less than12 connections to the LEC
Hybrid systems
Combines some features and functions of a PBX
with a keysystem
Used to handle requirements between those of a
PBX and keysystem
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Automatic Call Distributor
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Automatic Call Distributor
Used by large call centers to distribute
incoming calls to their operators
Used by telemarketing companies to place
outbound calls automatically
Predictive dialing software
System connects the next call with the next
available agent
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ACD and LAN
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ACD and LAN
Many inbound ACD installations also include the
installation of a local area network (LAN) for data
Calls received by the ACD can also include
information for the call center from the PSTN viaSS7
This information is used to provide the operator or
agent with information about the caller
Computer Telephony Integration (CTI) combinethese functions with the ACD in PC-based systems
T l i ti f D t
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Telecommunications for Data
Applications in Business
Need for special data communication
networks that tie all computers together
Local Area Networks (LANs)
Metropolitan Area Networks (MANs)
Wide Area Networks (WANs)
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LAN to WAN
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Local Area Networks (LANs)
80% of LANs use Ethernet to allow PCs to
access the network
PCs connected to Ethernet via two twisted-
pair copper wires
RJ-45 connectors terminate the four wires
Network Interface Card (NIC) in PC
Wiring hub serves as the Ethernet
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The Internet
Grown tremendously over the last two
decades
As much impact on society astelephone, television, and PC
National Information Infrastructure (NII)
U.S. Government program toestablish an information super highway
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Internet Timeline
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Key Internet Events
1961 - Leonard Kleinrock publishes paper on packet
switching
1969 - ARPANET test
1970 - Network Control Protocol (NCP) implemented onARPANET
1971 - E-mail
1974 - Kahn and Cerf publish paper on TCP/IP
1974 - 62 hosts on ARPANET 1979 - USENET newsgroup network
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Key Internet Events
1983 - Internet Activity Board (IAB) created to oversee
protocol development
1983 - TCP/IP version 4 adopted for ARPANET
1983 - 500 hosts 1984 - Domain Name System (DNS)
1986 - National Science Foundation Network (NSFNET)
1988 - Worm virus
1988 - Computer Emergency Response Team (CERT) 1990 - ARPANET retired
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Key Internet Events
1991 - Gopher menu-driven Intenet interface
1991 - Tim Berners-Lee develops World Wide Web
1992 - 1,000,000 hosts
1993 - Mosaic graphical WWW interface 1993 - Internet Network Information Center (InterNIC)
1993 - 2,000,000 hosts
1995 - NSF stops supporting NSFNET
Internet goes commercial
Internet Service Providers (ISPs)
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Key Internet Events
1995 - NSF starts supporting Very-High-Speed
Backbone Network Service (vBNS)
1996 - Telecommunications Act of 1996
1996 - 10,000,000 hosts 1997 to present - E-commerce, distance learning, Voice-
Over IP, Virtual Private Networks, Television-Over IP,
etc.
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The World Wide Web (WWW)
Organizes the resources of the Internet
Tim Berners-Lee
Hypertext Markup Language (HTML)
Hypertext Transport Protocol (HTTP)
Internet Engineering Task Force (IETF)
established standards for HTML and HTTP
Browsers based on HTML
Mosaic
Netscape
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Summary
Telecommunications means to communicate
over a distance using electrical signals, radio
waves, or light waves
Advances in technology have enabled the
PSTN to serve as a medium for the transfer
of voice, data, and video
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Telecommunications Jobs
Enormous growth in the job market for
telecommunications technicians, engineers, and
managers
Continual evolution of telecommunications technology Deregulation of the telecommunications industry
Explosive growth of personal computing
Need for LANs and WANs to connect PCs together
Increasing needs of information technology Growth of the Internet