Info Tech. IDevelopment of TelecommunicationsNetworks:

LANWANMAN

Mary Grace Satoya

Development of Telecommunications

Telecommunications

is the exchange of information over significant distances by electronic means.

Development of Telecommunication

From guttural sounds and facial expressions to body moves and gestures.

In addition, there has always been a need to communicate with others across an arbitrary distance, for instructions and orders while hunting etc.

There were three main means used:

Noise (megaphones, church bells, cannons etc.)optical effects (heliographs, watch towers and smoke signals, flashlights and semaphores)physical delivery (runners, horses, stage coaches, carrier pigeons, later on trains and other motor vehicles)

The First Big Breakthrough

Telegraph, invented in 1838, was taken into wide use six years later, in 1844, when Samuel F.B. Morse introduced his revolutionary new language - the Morse code. During the same year, the very first long-distance telegraph message was sent between Baltimore and Washington. What made telegraph such breakthrough was the incredible speed, at which data could be transmitted; nearly at the speed of light.

Distance Bandwidth- 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 was far superior compared to any of the earlier methods, due to its very high transmission speed. The intrinsic error rate of the telegraph was very low and, in case of errors, re-transmission was easy and quick. Also, telegraph was relatively cheap, and it was not man-power intensive.

Megaphone was a very unreliable transmission media, mainly due to its very limited range of about a mile or two, if the weather was good and there was little or no wind. Thus, it was very man-power intensive, if the distance between the endpoints was high. Transmission speed of the 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 step after the telegraph. Although the first telephone message ever was sent as early as 1876 (7 words, from one room to another) and, by 1890, many cities had primitive telephone systems. The first official trans-Atlantic message (90 words) took 67 minutes to cross the ocean. As of now, telephone is, by far, the most popular transmission media used.

The first trans-Atlantic wireless (radio) transmission was made in 1901; radio was a very expensive transmission media to use, its quality was very poor and the availability of radio links was very low. In short, radio was a very poor transmission media for critical data in its first years.

In 1956 more phone cables were installed across the Atlantic, Thus, the expensive and unreliable radio links were closed. Only a few months later, however, the radio links had to be reopened due to high demand. This, in part, triggered and encouraged the development of a reliable wireless transmission media. A demand, that was met in 1965, as the first commercial geostationary communications satellite Intelsat 1 (Early Bird), with 240 phone circuits, was launched.

The first trans-Atlantic fiber optic was laid in 1988. It was called TAT-8, and it carried 40000 telephone circuits. Some subsequent fiber optic cables include TAT-9 (1992, 80000 telephone circuits) and TAT-12 (1996, 300000 telephone circuits). Currently, there are 10 such cables in service and, another 10 under construction or planned.

Data networking1970's: limited long-distance (wide area networking) networks1980's: emergence of local area networks, with standards1990's: integration of the two - data networks became ubiquitous.

The main differences between Telecommunications and Data networking:

Telecommunications (referring mainly to voice transmission) medias are mainly circuit switched and the industry conservative. Data networking (referring mainly to data transmission) medias are mainly packet switched and the industry dynamic.

In information technology, a network is a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain sub networks

NETWORK

LAN(Local Area Network)

A local area network (LAN) is usually privately owned and links the devices in asingle office, building, or campus. Depending on the needs of an organization and the type of technology used.

5

WAN(Wide Area Network)

A wide area network (WAN) provides long-distance transmission of data, voice, image, and video information over large geographical areas that may comprise a country, a continent, or even the whole world.

MAN(Metropolitan Area Network)

A metropolitan area network (MAN) is designed to extend over an entire city. It may be a single network such as a cable television network, or it may be a means of connecting a number of LANs into a larger network so that resources may be shared LAN-to-LAN as well as device-to-device.