Chapter 1

Introduction to Telecommunications

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Objectives

Be able to explain what telecommunications is.

Have a basic understanding of the various networks used to transmit voice, video, and data signals from one location to another.

Know the types of media used to convey telecommunications signals between a sender and a receiver.

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Objectives (continued) Understand the basics of the three major

voice communication technologies (keysystem, private branch exchange, and automatic call distributor) available to a business enterprise and the type of business best served by each of these technologies.

Have a basic understanding of personal computer-based voice communication systems, referred to as computer telephony integrated (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 as analog (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. Bell’s 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 of the 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 along

with 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 local operator functions

Next were long distance operator functions Interactive-Voice-Response (IVR) systems

Collect calls Person-to-person Allow caller to provide information via scripted

questions Operators used to handle calls rejected by

automated 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 one

computer-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 purpose

integrated circuit chips Use of fiber optic cables for transmission

media 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 via SS7

This information is used to provide the operator or agent with information about the caller

Computer Telephony Integration (CTI) combine these functions with the ACD in PC-based systems

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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 as telephone, television, and PC

National Information Infrastructure (NII) – U.S. Government program to establish 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 on

ARPANET 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