01. History of telecommunications-2013-1.ppt

8/10/2019 01. History of telecommunications-2013-1.ppt

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History of

telecommunicationsIICT-BAS


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History of telecommunications

1809 - 'electrochemical' telegraph - German physician,anatomist and inventor Samuel Thomas von Smmering 1832 - electromagnetic telegraph - Baron Schilling,

Russia - short-distance transmission of signals betweentwo telegraphs in different rooms, tested on a 5 kmexperimental underground and underwater cable

1833 - Carl Friedrich Gauss and Wilhelm Weber,Germany - communicate over a distance of 1200 mwithin Gttingenachieve distant needle move in thedirection set by the commutator on the other end of theline

developed signals, own alphabet encoded in a binary codewhich was transmitted by positive or negative voltagepulses which were generated by means of moving aninduction coil up and down over a permanent magnet andconnecting the coil with the transmission wires by meansof the commutator


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1836David, American - the first known Americanelectric telegraph

1836 - the telegraph - developed by Samuel Morse (untilhe was 34, he was a painter!) and Alfred Vail (USA) -transmitting over long distances using poor quality wire;Vail - developed the Morse code signaling alphabet withMorse

1837 - the first commercial electrical telegraph - SirWilliam Fothergill Cooke and Charles Wheatstone,

Englandpatented as an alarm system; successfullydemonstrated Euston and Camden Town (London)


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1843 - U.S. Congress appropriated $30,000 to fund anexperimental telegraph line from Washington, D.C. toBaltimore

24 May 1844 - first public demonstration by Morse of histelegraph - a message from the Supreme Court

Chamber in Washington to the B&O Railroad inBaltimore 1861 - the first transcontinental telegraph system (USA) 1866 - the first successfultransatlantic telegraph cable

between Ireland and Newfoundland reduced communication time to a matter of a few hours,

allowing a message and a response in the same day !!!


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1861 - Johann Philipp Reis, Germany - firsttelephonecouldnt interest people in Germanyin his invention

1876Alexander Bell Bell's patent 174,465,was issued to Bell on March 7

Elisha Gray also experimenting with acoustic

telegraphy and files a patent application 3 hoursafter Bell with the U.S. Patent Office for atelephone - Bell got the patent


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1878 Microphone Edison (General Electric) 1878 - First Telephone Exchange in New

Haven, USA - 21 listings Mid-1880s - telephone exchanges in every

major city of the United States 1832, James Lindsay (UK) - classroom

demonstration of wireless telegraphy; 1854, hedemonstrated a transmission across the Firth of

Tay from Dundee to Woodhaven (3 km), usingwater as the transmission medium


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1884 Radio Telegraph Popov 1892 First Automatic Telephone Exchange in

La Porte USA by Strowger

1896 Radio Telegraph Marconi (Italy) 1898 First Automatic Telephone Exchange in

Germany

1901 Marconi - wireless communicationbetween Britain and Newfoundland, earned theNobel Prize in physics in 1909


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1918 Radio Carrier System /USA 1920 RadioBroadcasting

1925 John Baird, Scottish - demonstrated the

transmission of moving silhouette pictures inLondon

1929 - Bairds work formed the basis of semi-

experimental broadcasts done by the BritishBroadcasting Corporation


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1927demonstration of the cathode ray tube (CRT)in broadcasting of imagesCRT inventor was KarlBraun in 1897

1930 Coaxial cables

1931 Radiolinks

1937 Pulse Code Modulation - PCM (64kbps)

Reeves (Bell Labs) - representation of a signal by a

series of digital pulses firstly by sampling the signal,

quantizing it and then encoding ita method

developed in the seventies


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1945 - Arthur C. Clarkeproposes the ideafor Synchronous Orbit Satellites

1946 Cellular Radio (Bell Labs)remained

costly and not widely used until 1995

1947 Transistor (Bell Labs)

1957 Sputnik, USSRfirst satellite 1962Telstar - first active, direct relay

commercial communications satellite


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1960first LASER (Light Amplification by StimulatedEmission of Radiation) Theodore Maiman , USA

1960 - AT&T installs first electronic switching system

in Morris, IL 1961 - Electronic Telephone Exchange (Bell Labs); T-

1 Carrier System (Bell Labs) TDM (Time Domain

Multiplexing) - 24 channels = 64 Kbps, 1.544 Mbps(mega bits per sec)


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1965 - AT&T introduces stored programcontrolled switching

1966 - Fibre Glass optics - Kao & Hockman,Standard Telecom Labs

1967 - Larry Roberts paper proposing ARPANET,

Advanced Research Projects Agency

1969 - The Department of Defense initiates the

ARPANet, which led to the development of

Internet - initially computers at Stanford

University and UCLA are connected


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1969 ISDN (Integrated Services Digital Network2x64k+16k)

1970 Aloha-network (Hawaii)

1974 Packet and Circuit Switched data networks(CCITT X.25 and X.21) - International Telegraph and

Telephone Consultative Committee (CCITT,

from French: Comit Consultatif International Tlphonique etTlgraphique)


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1987 - Bellcore introduces the Asymmetric DigitalSubscriber Line (ADSL) concept which has thepotential of multimedia transmission over the nation'scopper loops

1989 HTTP/HTML in Cern by Tim Barners-Lee -Hypertext Transfer Protocol (a protocol i.e. set ofprocedures describing how to pass information)/HyperText Markup Language (language how to

present information that passes via HTTP)


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1991 - ATM (Asynchronous Transfer Mode 155

Mb/s)

1991 - IN CS.1 (Intelligent Networks) by ITU and

ETSI

1992 - WWW (World Wide Web) - the first audio

and video multicasts are broadcast over the

Internet 1993 - Internet browser MOSAIC is introduced at

the University of Illinois


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1998 GPRS (General Packet Radio System) 2001 UMTS (Universal Mobile

Telecommunication System)


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Terminal Complex First computer telecommunication systems -

early 60s: local multi-user systems - terminalcomplex

Classical Terminal Complex - shares computer

resources among closely located users viatelecommunication lines

Computer configuration (CPU / RAM / Channel

(usually phone line)) Transmission medium:

wires/cables: pairsor cableset of pairs; twisted pairsfor reduction of signal interference; coaxial cables(noise

shield)


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Terminal complex

CPU

RAM

I/O channel

I/O interface

Multiplexor

Telephone exchange

Link channels

Link channelsTerminal

...

Modem

Modem

Modem

ModemModemModem

I/O system

Modem

Modem

Modem

T

T

T

T

T

T


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Information transmission methods:

Synchronous: byte-stream forming data blocks,synchronization based on additional signals in control lines

synchro-symbols in the front and in the end of the block

advantage: higher speed, less communication overload drawback: more complicated hardware, buffer memory application: high speed communication

Asynchronous: 1 start impulse and 1 or 2 stop

impulse; clock frequency is higher than the read-write frequency (access instants) advantage: no buffering, simple synchronization circuit drawback: communication overload (30%) application: slow terminals in short distance

Terminal Complex


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Information transmission modes:

Terminal complexes use mostlyphone/telegraph lines on

switched lines: use the public exchange by

dialed access from point to point advantage: chipper drawback: slower, noisy

application: smaller traffic

leased lines: fixed lines for monopoly usefrom point to point; connection line is ownedof local PTT company

advantage: reliable error-free, faster, promptness

drawback: price

application: bigger traffic

Terminal Complex


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Terminal Complex Standard Interface

usually bus of 30-60 signal lines physical parameters: line length; signal

parameters (amplitude, frequency, workingmode: monopoly, multiplex, block-multiplex);multiplexors number

Multiplexor: transforms parallel (byte) stream from terminals

to sequential (bit) stream for the channelinterface

addressing the terminals - 2 methods: cycletime-driven or event driven selection

error control

same functions in opposite direction (from

channel to terminals)


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Terminal Complex Modems (signal MODulator/DEModulator)

phone line transmission with digital to analogand analog to digital conversion

Structure and components: Modulator (data input)

Demodulator (data output) Filter (frequency separator)

Linear Amplifier

Modulation types AM FM

PhM


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Modulations

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01. History of telecommunications-2013-1.ppt