Info Tech. IDevelopment of TelecommunicationsNetworks: LAN WAN MAN Mary Grace Satoya
Telecommunications is the exchange of informationover significant distances by electronicmeans.
Development of TelecommunicationFrom guttural sounds and facialexpressions to body moves and gestures.In addition, there has always been aneed to communicate with others acrossan arbitrary distance, for instructions andorders while hunting etc.
There were three main means used:Noise (megaphones, church bells, cannonsetc.)optical effects (heliographs, watch towers andsmoke signals, flashlightsand semaphores)physical delivery(runners, horses, stage coaches,carrier pigeons, later on trains andother motor vehicles)
The First Big Breakthrough Telegraph, invented in 1838, wastaken into wide use six years later, in1844, when Samuel F.B.Morse introduced his revolutionary newlanguage - the Morse code. During thesame year, the very first long-distancetelegraph message was sentbetween Baltimore and Washington.What made telegraph such breakthroughwas the incredible speed, at which datacould be transmitted; nearly at the speedof light.
DistanceBandwidth- between distanceMethod Data rate Msg speed "repeaters" product-----------------------------------------------------------------------------Carrier pigeon ~10 kbit/pigeon 70 km/h 700 km 150 kbit-m/secMegaphone 100 bits/sec 1000 km/h 2 km 30 bit-km/sec (but many repeaters)Train Very high/train 70 km/h Virtually very high zeroTelegraph 100 bits/sec Very high 20 km 1 kbit-km/sec
With short messages, telegraph wasfar superior compared to any of theearlier methods, due to its veryhigh transmission speed. The intrinsicerror rate of the telegraph was very lowand, in case of errors, re-transmissionwas easy and quick. Also, telegraph wasrelatively cheap, and it was not man-power intensive.
Megaphone was a very unreliabletransmission media, mainly due to its verylimited range of about a mile or two, if theweather was good and there was little or nowind. Thus, it was very man-powerintensive, if the distance between theendpoints was high. Transmission speed ofthe megaphone was relatively high -the speed of sound or, 1000 km/h .
Telephone, Radio, Satellites and Fiber optic cables
Telephone was a rather logical next stepafter the telegraph.Although the first telephone message ever wassent as early as 1876 (7 words, from one roomto another) and, by 1890, many cities hadprimitive telephone systems. Thefirst official trans-Atlantic message (90 words)took 67 minutes to cross the ocean.As of now, telephone is, by far, the mostpopular transmission media used.
The first trans-Atlantic wireless (radio)transmission was made in 1901; radio was avery expensive transmission media to use,its quality was very poor and the availabilityof radio links was very low. In short, radiowas a very poor transmission media forcritical data in its first years.
In 1956 more phone cables were installedacross the Atlantic, Thus, the expensive andunreliable radio links were closed. Only a fewmonths later, however, the radio links had to bereopened due to high demand. This, inpart, triggered and encouraged thedevelopment of a reliable wireless transmissionmedia. A demand, that was met in 1965, as thefirst commercial geostationary communicationssatellite Intelsat 1 (Early Bird), with 240 phonecircuits, was launched.
The first trans-Atlantic fiber optic waslaid in 1988. It was called TAT-8, and it carried40000 telephone circuits. Some subsequentfiber optic cables include TAT-9 (1992, 80000telephone circuits) and TAT-12 (1996, 300000telephone circuits). Currently, there are 10such cables in service and, another 10 underconstruction or planned.
Data networking1970s: limited long-distance (widearea networking) networks1980s: emergence of local areanetworks, with standards1990s: integration of the two - datanetworks became ubiquitous.
The main differences betweenTelecommunications and Data networking:Telecommunications (referring mainly tovoice transmission) medias are mainly circuitswitched and the industry conservative.Data networking (referring mainly to datatransmission) medias are mainly packetswitched and the industry dynamic.
NETWORK In information technology, a networkis a series of points or nodesinterconnected by communication paths.Networks can interconnect with othernetworks and contain sub networks
LAN (Local Area Network) A local area network (LAN) isusually privately owned and linksthe devices in asingleoffice, building, or campus.Depending on the needs of anorganization and the type oftechnology used.
WAN (Wide Area Network) A wide area network (WAN)provides long-distancetransmission of data, voice, image,and video information over largegeographical areas that maycomprise a country, a continent, oreven the whole world.
MAN (Metropolitan Area Network) A metropolitan area network(MAN) is designed to extend over anentire city. It may be a single networksuch as a cable televisionnetwork, or it may be a meansof connecting a number of LANs intoa larger network so that resourcesmay be shared LAN-to-LAN as wellas device-to-device.