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Friday, 28 October 2011

A Brief History of Telecommunication

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A Brief History of Telecommunication
by matt_bird on 25-10-2011 11:19 - last edited on 27-10-2011 18:45

A Brief History of Telecommunication

Part One


Here we are going to take a look at how the mobile phone has become the world’s most popular gadget. There are reckoned to be 1.4 billion televisions on the planet but the humble mobile, numbers at least three times that (figures for 2008). By the end of 2012 there will be more mobiles in the world than there are people according to the Institute of Engineering & Technology.

It was as recently as 1985 that the very first handsets were released in the UK by Vodaphone and then Cellnet (later to become o2), they were cumbersome devices weighing up to 20kg because the battery systems available at the time were so basic. We had the comical sight of all these high powered businessman types staggering about carrying two briefcases, one of which had a veritable jungle of cables attached to it and we all said 'that will never catch on'. How wrong we were.

Telephony or telecoms really began in 1838 when Samuel Morse invented his system of dots and dashes for letters of the alphabet, which allowed complex messages to be sent and received. It took him another six years to get the necessary support from Congress to actually install the world’s first telegraph line made with copper cable, between Washington and Baltimore a distance of around forty miles.

From this point on copper wires began to link all the larger Cities and towns across the US with most of these wires being built and operated by Western Union, who are still active with near instant global money transfer today. Similar systems were being built across Europe as well and these allowed the near instant transmission of messages.

In 1851 the first undersea (copper) cable was laid between England and France and in 1858 the first Trans-Atlantic cable was laid. The depths involved made this Anglo US venture the major engineering task of its' time and it took five attempts before an unbroken cable was finished. Unfortunately this cable was cooked by an over enthusiastic engineer sending too many volts through it and it failed after just three weeks. In 1865 it was tried for a second time and 1200 miles was laid before the cable broke and was unable to be retrieved. The third cable was laid by Brunels' Great Eastern and went without a hitch, the 1686 nautical miles between Ireland and Newfoundland was laid at the rate of 120 nautical miles per day. After this the Great Eastern managed to find the end of the second cable at a depth of 16,000ft, raised and spliced it so now there were now 2 working Transatlantic cables.


Map of the 1858 cable route


The next major development was made in 1876 by Alexander Graham Bell, a Scotsman in Boston, with his 'Liquid Transmitter' so called as it worked with a diaphragm vibrating a needle in water to vary the electrical current in the circuit. This device allowed him to make the first ever voice call over a wire although it was only between two rooms. It took Bell a further five months to refine the invention to carry his voice over five miles. Western Union helped develop their Morse telegraphy system into the copper cable telephone network we know so well.


A replica of the 'Liquid Transmitter'

In 1880 Bell also made the first wireless communications with his 'Photophone'. It used a beam of light to carry a sound signal between two buildings 215 metres apart and was considered by Bell his most important invention. Due to its use of an atmospheric medium it failed to produce real advances until the development of Optical technologies by the US military in the 1920s. The theory of "LASER" was advanced by Einstein in 1917, however it took many years before a working model was produced.

It took until after the Second World War for a wireless telephone as we understand them to be developed in the US by AT&T. They were very simple devices much like a walkie talkie in that only one user could speak at a time, and you had to manually search the frequencies of the radio spectrum at 35mhz or 150mhz to find space for the call. At this time the batteries necessary made the device weigh 35kg.

In the UK it was the General Post Office who built and operated our telegraph / telephone infrastructure with the first commercial calls being made in 1912. This network was built with copper cables. In 1981 the GPO was split into the Post Office and British Telecoms. BT was the parent company of Cellnet to give them an entry into the lucrative mobiles market and BTCellnet later became O2 who in turn are parents to giffgaff.

In 1970 optical fibre was invented by Corning Glass Works and proved able to send signal at 45Mbps although it was necessary to have signal boosters every 10kms. By 1981 Single-Mode fibre was found to be the way forward with great improvements and by 1987 these 2nd generation fibres were operating at speeds over 1.5Gb/s with boosters only needed every 50km, In 1988 the first Transatlantic fibre was laid. The 3rd generation upped the speeds to 2.5Gb/s and halved the need for boosters to 100kms apart.


By 1992 and 4th generation fibre the invention of optical amplifiers and Wavelength Division Multiplexing has enabled speeds to double every 6 months and by 2006 transmission speed was up to 14Tb/s using amplifiers only every 160kms.

To put optical transmission in its simplest terms think of an LED, a light emitting diode, this produces 'incoherent light', a laser emitting diode produces 'coherent light' and WDM means sending more laser light beams down a single fibre.

This is how cable TV and broadband services are delivered in towns and cities and due to the high costs of these technologies means it will never be viable to send fibre to the more rural parts of our country. This is one of the many reasons for the explosion in demand for mobile internet which we will look at more next time.

Thank you very much for reading,

Matt


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