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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