History of X-Ray

Wilhelm Conrad Röntgen

The first x-ray
Frau Röntgen's left hand

In October of 1895, Wilhelm Conrad Röntgen (1845-1923) who was professor of physics and the director of the Physical Institute of the University of Wurburg, became interested in the work of Hillorf, Crookes, Hertz, and Lenard. The previous June, he had obtained a Lenard tube from Muller and had already repeated some of the original experiments that Lenard had created. He had observed the effects Lenard had as he produced cathode rays in free air. He became so fascinated that he decided to forego his other studies and concentrate solely on the production of cathode rays. One Friday evening, on November 8, 1895, he worked alone in his laboratory. It was the beginning of the weekend and all of his assistants had gone home. He had set up his experiment using a Crookes tube fitted with an anode and cathode, separated from each other by a few centimeters in the tube. He used a Rhumkoff induction coil to produce a difference of potential of a few thousand volts, knowing that a stream of charged particles would originate in the cathode and would be attracted to the anode.

The laboratory Röntgen worked in that evening was very similar to all other laboratories of those who worked before him, but the conditions that existed that evening varied in three very important ways. His laboratory was dark, his tube was covered with a light-proof cardboard jacket and a screen of fluorescent material laid on a table a few feet away from the apparatus. While passing the discharge, he suddenly noticed a shimmering light on the table top. He could not believe his eyes, so he again repeated the experiment. He released the discharge many times producing the same results each time. Greatly excited, he realized that the green fluorescence was emanating from the screen. He repeated the experiment again, this time moving the screen further and further away and he still received the same results.

Röntgen knew the fluorescence could not be produced by the cathode rays since it was well known that they could not penetrate through the wall of the tube. Visible light could not be the stimulus since the tube was covered with a shield which was opaque to light. He boldly hypothesized that he must have been producing some unknown type of radiation.

Röntgen spent the next eight weeks in his laboratory repeating his experiments. He ate and even slept in his laboratory as he attempted to determine if the rays could penetrate substances besides the air. He placed various objects between the tube and screen and he found that the screen still fluoresced but with different intensities depending on the material being used. When he placed a lead disk, which he was holding, in the cathode ray path he was astonished to find the shadow of the round circle appeared on the screen along with the outline of his thumb and forefinger and within them the bones of his hand! He replaced the screen with a photographic plate and employed his wife Bertha (Frau Röntgen) to place her hand on the photographic plate while he directed the rays at it for fifteen minutes.

Röntgen hurriedly prepared his notes so that his first report "On a New Kind of Rays" could be published in the Proceedings of the Physical Medical Society of Wurburg on December 28, 1895. Not knowing what these emanations were he uses the term x-ray to describe the rays he was producing. Later, in 1896, he accepted the Rumford gold medal of the Royal Society and in 1901 he would be the first to receive the Nobel Prize for physics, but he bequeathed the Nobel prize money to scientific research at Wurzburg.

History of Television

The television has become such an integral part of homes in the modern world that it is hard to imagine life without television. The boob tube, as television is also referred to, provides entertainment to people of all ages. Not just for entertainment value, but TV is also a valuable resource for advertising and different kinds of programming.

The television as we see it and know it today was not always this way. Let’s take a brief look at the history of television and how it came into being.

Timeline of TV History

Different experiments by various people, in the field of electricity and radio, led to the development of basic technologies and ideas that laid the foundation for the invention of television.

In the late 1800s, Paul Gottlieb Nipkow, a student in Germany, developed the first ever mechanical module of television. He succeeded in sending images through wires with the help of a rotating metal disk. This technology was called the ‘electric telescope’ that had 18 lines of resolution.

Around 1907, two separate inventors, A.A. Campbell-Swinton from England and Russian scientist Boris Rosing, used the cathode ray tube in addition to the mechanical scanner system, to create a new television system.

From the experiments of Nipkow and Rosing, two types of television systems came into existence: mechanical television and electronic television.

Mechanical Television History

In 1923, an American inventor called Charles Jenkins used the disk idea of Nipkow to invent the first ever practical mechanical television system. By 1931, his Radiovisor Model 100 was being sold in a complete kit as a mechanical television.

In 1926, just a little after Jenkins, a British inventor known as John Logie Baird, was the first person to have succeeded in transmitting moving pictures through the mechanical disk system started by Nipkow. He also started the first ever TV studio.

From 1926 till 1931, the mechanical television system saw many innovations. Although the discoveries of these men in the department of mechanical television were very innovative, by 1934, all television systems had converted into the electronic system, which is what is being used even today.

Electronic Television History

The experiments of Swinton in 1907, with the cathode ray tube for electronic television held great potential but were not converted into reality. Finally, in 1927, Philo Taylor Farnsworth was able to invent a working model of electronic television that was based on Swinton’s ideas.

His experiments had started when he was just a little boy of 14 years. By the time he became 21, Philo had created the first electronic television system, which did away with the rotating disks and other mechanical aspects of mechanical television. Thus was born the television system which is the basis of all modern TVs.

All the early television systems were black and white, with color television being invented much later on. Since the early invention of television in the beginning of the 1900s, history has seen many firsts in the area of television.

History of Trains

The History of Train transport dates back nearly 500 years, and includes systems with man or horse power and rails of wood or stone. Modern rail transport systems first appeared in England in the 1820s. These systems, which made use of the steam locomotive, were the first practical forms of mechanized land transport, and they remained the primary form of mechanized land transport for the next 100 years.

Ancient world
The earliest evidence of a railway found thus far was the 6 to 8.5 km long Diolkos wagonway, which transported boats across the Isthmus of Corinth in Greece since around 600 BC. Wheeled vehicles pulled by men and animals ran in grooves in limestone, which provided the track element, preventing the wagons from leaving the intended route. The Diolkos was in use for over 650 years, until at least the 1st century AD. The first horse-drawn wagonways also appeared in ancient Greece, with others to be found on Malta and various parts of the Roman Empire, using cut-stone tracks.

Early railways
Wagonways or tramways are thought to have developed in Germany in the 1550s to facilitate the transport of ore tubs to and from mines, utilising primitive wooden rails. Such an operation was illustrated in 1556 by Georgius Agricola. The technology spread across Europe and had certainly arrived in Britain by the early 1600s. The Wollaton Wagonway was probably the earliest British installation, completed in 1604 , and recorded as running from Strelley to Wollaton near Nottingham. Another early wagonway is noted at Broseley in Shropshire from 1605 onwards. Huntingdon Beaumont (who was concerned with mining at Strelley) also laid down broad wooden rails near Newcastle upon Tyne, on which a single horse could haul fifty or sixty bushels of coal. By the eighteenth century, such wagonways and tramways existed in a number of areas. Ralph Allen, for example, constructed a tramway to transport stone from a local quarry to supply the needs of the builders of the Georgian terraces of Bath. The Battle of Prestonpans, in the Jacobite Rebellion, was fought astride a wagonway. This type of transport spread rapidly through the whole Tyneside coal-field, and the greatest number of lines were to be found in the coalfield near Newcastle upon Tyne, where they were known locally as wagonways. Their function in most cases was to facilitate the transport of coal in chaldron wagons from the coalpits to a staithe (a wooden pier) on the river bank, whence coal could be shipped to London by collier brigs. The wagonways were engineered so that trains of coal wagons could descend to the staith by gravity, being braked by a brakesman, who rode in the rear vehicle, known as a dandy cart. This also conveyed a horse, which was used to pull the empty wagons back to the colliery. Because rails were smoother than roads, a greater quantity and tonnage of bulk goods such as coal and minerals could be carried, and without damage to highways. Naturally, a great deal of inventiveness was focussed upon improving the rails and reducing the degree of friction between wheel and rail. In the late 1760s, the Coalbrookdale Company began to fix plates of cast iron to the wooden rails. These (and earlier railways) had flanged wheels as on modern railways, but another system was introduced, in which unflanged wheels ran on L-shaped metal plates - these became known as plateways. John Curr, a Sheffield colliery manager, invented this flanged rail, though the exact date of this is disputed. William Jessop, a civil engineer, used a form of edge rails successfully on a scheme at Nanpantan, Loughborough, Leicestershire in 1789, so he and his partner Benjamin Outram started manufacturing iron edge rails in 1790. As the colliery and quarry tramways and wagonways grew longer, the possibility of using the technology for the public conveyance of goods suggested itself. On 26 July 1803, Jessop opened the Surrey Iron Railway in south London - arguably, the world's first public railway, albeit a horse-drawn one. It was not a railway in the modern sense of the word, as it functioned like a turnpike road. There were no official services, as anyone could bring a vehicle on the railway by paying a toll. It was not until 1825 that the success of the Stockton and Darlington Railway proved that the railways could be made as useful to the general shipping public as to the colliery owner. This railway broke new ground by using rails made of rolled wrought iron, produced at Bedlington Ironworks in Northumberland. Such rails were stronger. This railway linked the town of Darlington with the port of Stockton-on-Tees, and was intended to enable local collieries (which were connected to the line by short branches) to transport their coal to the docks. As this would constitute the bulk of the traffic, the company took the important step of offering to haul the colliery wagons or chaldrons by locomotive power, something that required a scheduled or timetabled service of trains. However, the line also functioned as a toll railway, where private horse drawn wagons could be operated upon it. This curious hybrid of a system (which also included, at one stage, a horse drawn passenger wagon) could not last, and within a few years, traffic was restricted to timetabled trains. (However, the tradition of private owned wagons continued on railways in Britain until the 1960s.)

 

Steam power train introduced
James Watt, a Scottish inventor and mechanical engineer, was responsible for improvements to the steam engine of Thomas Newcomen, hitherto used to pump water out of mines. Watt developed a reciprocating engine, capable of powering a wheel. Although the Watt engine powered cotton mills and a variety of machinery, it was a large stationary engine. It could not be otherwise; the state of boiler technology necessitated the use of low pressure steam acting upon a vacuum in the cylinder, and this mode of operation needed a separate condenser and an air pump. Nevertheless, as the construction of boilers improved, he investigated the use of high pressure steam acting directly upon a piston. This raised the possibility of a smaller engine, that might be used to power a vehicle, and he actually patented a design for a steam locomotive in 1784. His employee William Murdoch produced a working model of a self propelled steam carriage in that year. The first steam locomotive was built in 1804 by Richard Trevithick, an English engineer born in Cornwall. (The story goes that it was constructed to satisfy a bet by Samuel Homfray, the local iron master.) This used high pressure steam to drive the engine by one power stroke. (The transmission system employed a large fly-wheel to even out the action of the piston rod.) His locomotive had no name, and was used on the Merthyr Tydfil Tramroad in South Wales (sometimes - but incorrectly - called the Penydarren Tramroad).Trevithick later demonstrated a locomotive operating upon a piece of circular track in Bloomsbury, London, the "Catch-Me-Who-Can", but never got beyond the experimental stage with railway locomotives, not least because his engines were too heavy for the cast-iron plateway track then in use. Despite his inventive talents, Richard Trevithick died in poverty, with his achievement being largely unrecognized. The impact of the Napoleonic Wars resulted in (amongst other things) a dramatic rise in the price of fodder. This was the imperative that made the locomotive an economic proposition, if it could be perfected. The first commercially successful steam locomotive was Matthew Murray's rack locomotive The Salamanca built for the narrow gauge Middleton Railway in 1812. This twin cylinder locomotive was not heavy enough to break the edge-rails track, and solved the problem of adhesion by a cog-wheel utilising slots cast in one of the rails. It was the first rack railway. This was followed in 1813 by the Puffing Billy built by Christopher Blackett and William Hedley for the Wylam Colliery Railway, the first successful locomotive running by adhesion only. This was accomplished by the distribution of weight by a number of wheels. Puffing Billy is now on display in the Science Museum in London, the oldest locomotive in existence. In 1814 George Stephenson, inspired by the early locomotives of Trevithick, Murray and Hedley, persuaded the manager of the Killingworth colliery where he worked to allow him to build a steam-powered machine. He built the Blücher, one of the first successful flanged-wheel adhesion locomotives. Stephenson played a pivotal role in the development and widespread adoption of the steam locomotive. His designs considerably improved on the work of the earlier pioneers. In 1825 he built the Locomotion for the Stockton and Darlington Railway which became the first public steam railway in the world.

The Birth of the Railway
In 1812 Oliver Evans, a United States engineer and inventor, published his vision of what steam railways could become, with cities and towns linked by a network of long distance railways plied by speedy locomotives, greatly reducing the time required for personal travel and for transport of goods. Evans specified that there should be separate sets of parallel tracks for trains going in different directions. Unfortunately, conditions in the infant United States did not enable his vision to take hold. This vision had its counterpart in Britain, where it proved to be far more influential. William James, a rich and influential surveyor and land agent, was inspired by the development of the steam locomotive to suggest a national network of railways. He was responsible for proposing a number of projects that later came to fruition, and he is credited with carrying out a survey of the Liverpool and Manchester Railway. Unfortunately, he became bankrupt and his schemes were taken over by George Stephenson and others. However, he is credited by many historians with the title of "Father of the Railway". The success of the Stockton and Darlington encouraged the rich investors of the rapidly industrialising North West of England to embark upon a project to link the rich cotton manufacturing town of Manchester with the thriving port of Liverpool. The Liverpool and Manchester Railway was the first modern railway, in that both the goods and passenger traffic was operated by scheduled or timetabled locomotive hauled trains. At the time of its construction, there was still a serious doubt that locomotives could maintain a regular service over the distance involved. A widely reported competition was held in 1829 called the Rainhill Trials, to find the most suitable steam engine to haul the trains. A number of locomotives were entered, including Novelty, Perseverance, and Sans Pareil. The winner was Stephenson's Rocket, which had superior steaming qualities as a consequence of the installation of a multi-tubular boiler (suggested by Henry Booth, a director of the railway company). The promoters were mainly interested in goods traffic, but after the line opened on 15 September, 1830, they found to their amazement that passenger traffic was just as remunerative. The success of the Liverpool and Manchester railway influenced the development of railways elsewhere in Britain and abroad. The company hosted many visiting deputations from other railway projects, and many railwaymen received their early training and experience upon this line. It must be remembered that the Liverpool and Manchester line was still a short one, linking two towns within an English shire county. The world's first trunk line can be said to be the Grand Junction Railway, opening in 1837, and linking a mid point on the Liverpool and Manchester Railway with Birmingham, by way of Crewe, Stafford, and Wolverhampton.

Further Development
The earliest locomotives in revenue service were small four-wheeled locos similar to the Rocket. However, the inclined cylinders caused the engine to rock, so they first became horizontal and then, in his "Planet" design, were mounted inside the frames. While this improved stability, the "crank axles" were extremely prone to breakage. Greater speed was achieved by larger driving wheels at expense of a tendency for wheel slip when starting. Greater tractive effort was obtained by smaller wheels coupled together, but speed was limited by the fragility of the cast iron connecting rods. Hence, from the beginning, there was a distinction between the light fast passenger loco and the slower more powerful goods engine. Edward Bury, in particular, refined this design and the so-called "Bury Pattern" was popular for a number of years, particularly on the London and Birmingham. Meanwhile by 1840 Stephenson had produced larger, more stable, engines in the form of the 2-2-2 "patentee" and six-coupled goods engines. Locomotives were travelling longer distances and being worked more extensively. The North Midland Railway expressed their concern to Robert Stephenson who was, at that time, their general manager, about the effect of heat on their fireboxes. After some experiments, he patented his so-called Long Boiler design. These became a new standard and similar designs were produced by other manufacturers, particularly Sharp Brothers whose engines became known affectionately as "Sharpies" The longer wheelbase for the longer boiler produced problems in cornering. For his six-coupled engines, Stephenson removed the flanges from the centre pair of wheels. For his express engines, he shifted the trailing wheel to the front in the 4-2-0 formation, as in his "Great A." There were other problems. One was that the firebox was restricted in size, or had to be mounted behind the wheels. The other was that, the generally held opinion arose that, to improve stability, the centre of gravity should be kept low. The most extreme outcome of this was the Crampton locomotive which mounted the driving wheels behind the firebox and could be made very large in diameter. These achieved the hitherto unheard of speed of 70mph but were very prone to wheelslip. With their long wheelbase, they were unsuccessful on Britain's winding tracks, but became popular in the USA and France, where the popular expression became to "prendre le Crampton". John Gray of the London and Brighton Railway was one who disbelieved the necessity for a low centre of gravity and produced a series of locos that were much admired by David Joy who developed the design at the firm of E. B. Wilson and Company to produce the 2-2-2 Jenny Lind locomotive, one of the most successful passenger locomotives of its day. Meanwhile the Stephenson 0-6-0 Long Boiler locomotive with inside cylinders became the archetypical goods engine

Expanding network
Railways quickly became essential to the swift movement of goods and labour that was needed for industrialization. In the beginning, canals were in competition with the railroads, but the railroads quickly gained ground as steam and rail technology improved, and railroads were built in places where canals were not practical. By the 1850s, many steam-powered railways had reached the fringes of built-up London. But the new lines were not permitted to demolish enough property to penetrate the City or the West End, so passengers had to disembark at Paddington, Euston, Kings Cross, Fenchurch Street, Charing Cross, Waterloo or Victoria and then make their own way via hackney carriage or on foot into the centre, thereby massively increasing congestion in the city. A Metropolitan Railway was built under the ground to connect several of these separate railway terminals, and thus became the world's first "Metro."

In 1869, the symbolically important trans-continental railroad was completed in the United States with the driving of a golden spike.

Electric railways revolutionizes urban transport
Prior to the development of electric railways, most overland transport aside from the railways had consisted primarily of horse powered vehicles. Placing a horse car on rails had enabled a horse to move twice as many people, and so street railways were born. In January of 1888, Richmond, Virginia served as a proving grounds for electric railways as Frank Sprague built the first working electric streetcar system there. By the 1890s, electric power became practical and more widespread, allowing extensive underground railways. Large cities such as London, New York, and Paris built subway systems. When electric propulsion became practical, most street railways were electrified. These then became known as "streetcars," "trolleys," "trams" and "Strassenbahn." In many countries, these electric street railways grew beyond the metropolitan areas to connect with other urban centers. In the USA, "electric interurban" railroad networks connected most urban areas in the states of Illinois, Indiana, Ohio, Pennsylvania and New York. In Southern California, the Pacific Electric Railway connected most cities in Los Angeles and Orange Counties, and the Inland Empire. There were similar systems in Europe. One of the more notable rail systems connected every town and city in Belgium. One of the more notable tramway systems in Asia is the Hong Kong Tramways, which started operation in 1904 and run exclusively on double-decker trams. The remnants of these systems still exist, and in many places they have been modernized to become part of the urban "rapid transit" system in their respective areas. In the past thirty years increasing numbers of cities have restored electric rail service by building "light rail" systems to replace the tram system they removed during the mid-20th century.

Diesel power
Diesel-electric locomotives could be described as electric locomotives with an on-board generator powered by a diesel engine. The first diesel locomotives were low-powered machines, diesel-mechanical types used in switching yards. Diesel and electric locomotives are cleaner, more efficient, and require less maintenance than steam locomotives. They also required less specialized skills in operation and their introduction diminished the power of railway unions in the USA (one of the earliest countries to adopt diesel power on a wide scale). By the 1970s, diesel and electric power had replaced steam power on most of the world's railroads. In the 20th century, road transport and air travel replaced railroads for most long-distance passenger travel in the United States, but railroads remain important for hauling freight in the United States, and for passenger transport in many other countries. In rail transport, a train is a series of rail vehicles that move along guides to transport freight or passengers from one place to another. The guideway (permanent way) usually consists of conventional rail tracks, but might also be monorail or maglev. Propulsion for the train is provided by a separate locomotive, or from individual motors in self-propelled multiple units. Most trains are powered by diesel engines or by electricity supplied by trackside systems. Historically the steam engine was the dominant form of locomotive power through the mid-20th century, but other sources of power (such as horses, rope, wire, gravity, pneumatics, or gas turbines) are possible. The word 'train' comes from the Old French trahiner, itself from the Latin trahere 'pull, draw'.

There are various types of train designed for particular purposes.
A train can consist of a combination of one or more locomotives and attached railroad cars, or a self-propelled multiple unit (or occasionally a single powered coach, called a railcar). Trains can also be hauled by horses, pulled by a cable, or run downhill by gravity. Special kinds of trains running on corresponding special 'railways' are atmospheric railways, monorails, high-speed railways, maglev, rubber-tired underground, funicular and cog railways. A passenger train may consist of one or several locomotives, and one or more coaches. Alternatively, a train may consist entirely of passenger carrying coaches, some or all of which are powered as a "multiple unit". In many parts of the world, particularly Japan and Europe, high-speed rail is utilized extensively for passenger travel. Freight trains comprise wagons or trucks rather than carriages, though some parcel and mail trains (especially Travelling Post Offices) are outwardly more like passenger trains. Trains can also be 'mixed', comprising both passenger accommodation and freight vehicles. Such mixed trains are most likely to occur where services are infrequent, and running separate passenger and freight trains is not cost-effective. However, the differing needs of passengers and freight usually means this is avoided where possible. Special trains are also used for track maintenance; in some places, this is called maintenance of way. In the United Kingdom, a train hauled by two locomotives is said to be "double-headed", and in Canada and the United States it is quite common for a long freight train to be headed by three, four, or even five locomotives. A train with a locomotive attached at each end is described as 'top and tailed', this practice typically being used when there are no reversing facilities available. Where a second locomotive is attached temporarily to assist a train up steep banks or grades (or down them by providing braking power) it is referred to as 'banking' in the UK, or 'helper service' in North America. Recently, many loaded trains in the US have been made up with one or more locomotives in the middle or at the rear of the train, operated remotely from the lead cab. This is referred to as "DP" or "Distributed Power."

Official terminology
The railway terminology that is used to describe a 'train' varies between countries.

 

Motive power
The first trains were rope-hauled, gravity powered or pulled by horses, but from the early 19th century almost all were powered by steam locomotives. From the 1920s onwards they began to be replaced by less labour intensive and cleaner (but more complex and expensive) diesel locomotives and electric locomotives, while at about the same time self-propelled multiple unit vehicles of either power system became much more common in passenger service. Most countries had replaced steam locomotives for day-to-day use by the 1970s, usually with diesel locomotives. A few countries, most notably the People's Republic of China, where coal and labour are cheap, still use steam locomotives, but this is being gradually phased out. Historic steam trains still run in many other countries, for the leisure and enthusiast market. Electric traction offers a lower cost per mile of train operation but at a very high initial cost, which can only be justified on high traffic lines. Since the cost per mile of construction is much higher, electric traction is less favored on long-distance lines with the exception of long-distance high speed lines. Electric trains receive their current via overhead lines or through a third rail electric system.

Passenger train
A passenger train is one which includes passenger-carrying vehicles. It may be a self-powered multiple unit or railcar, or else a combination of one or more locomotives and one or more unpowered trailers known as coaches, cars or carriages. Passenger trains travel between stations where passengers may join or leave the train. Many of the more prestigious passenger train services have been given a specific name, some of which have become famous in literature and fiction. India has the largest passenger density in the world.

Long-distance train
Long-distance trains travel between many cities and/or regions of a country, and sometimes cross several countries. They often have a dining car or restaurant car to allow passengers to have a meal during the course of their journey. Trains traveling overnight may also have sleeping cars. Very long distance trains such as those on the Trans-Siberian railway are usually not high-speed.

High-speed train
High speed trains normally travel during the day. They compete with airliners in speed. In Japan, most of the public transportation between the Tokyo metropolitan area and the Osaka metropolitan area (with around 500 km in distance between them) is dominated by the Shinkansen, however in travel further than around 500 km (such as Tokyo-Hiroshima) more people prefer to travel by air. Very fast trains sometimes tilt, like the APT, the Pendolino, or the Talgo. Tilting is a system where the passenger cars automatically lean into curves, reducing the centrifugal forces acting sideways on passengers and permitting higher speeds on curves in the track with greater passenger comfort.

Inter-city train
For trains connecting cities, we can distinguish inter-city trains, which do not halt at small stations, and trains that serve all stations, usually known as local trains or "stoppers" (and sometimes an intermediate kind, see also limited-stop).

Branch line train
Connections to local stations or local lines and are usually stopping services, running usually to all stations or the majority of stations on a line.

Commuter train
For shorter distances many cities have networks of commuter trains, serving the city and its suburbs. Some carriages may be laid out to have more standing room than seats, or to facilitate the carrying of prams, cycles or wheelchairs. Some countries have double-decked passenger trains for use in conurbations. Double deck high speed and sleeper trains are becoming more common in Europe. Passenger trains usually have emergency brake handles (or a "communication cord") that the public can operate. Abuse is punished by a heavy fine. Large cities often have a metro system, also called underground, subway or tube. The trains are electrically powered, usually by third rail, and their railroads are separate from other traffic, without level crossings. Usually they run in tunnels in the city center and sometimes on elevated structures in the outer parts of the city. They can accelerate and decelerate faster than heavier, long-distance trains. A light one- or two-car rail vehicle running through the streets is by convention not considered a train but rather a tram, trolley, light-rail vehicle or streetcar, but the distinction is not always strict. In some countries such as the United Kingdom the distinction between a tramway and a railway is precise and defined in law. The term light rail is sometimes used for a modern tram, but it may also mean an intermediate form between a tram and a train, similar to metro except that it may have level crossings. These are often protected with crossing gates. They may also be called a trolley. Maglev trains and monorails represent minor technologies in the train field. The term rapid transit is used for public transport such as commuter trains, metro and light rail. However, in New York City, lines on the New York City Subway have been referred to as "trains".

Named train
Railway companies often give a name to a train service as a marketing exercise, to raise the profile of the service and hence attract more passengers (and also to gain kudos for the company). Usually, naming is reserved for the most prestigious trains: the high-speed express trains between major cities, stopping at few intermediate stations. The names of services such as the Orient Express, the Flying Scotsman, the Flèche d’Or and the Royal Scot have passed into popular culture.

Freight train
A freight train (or goods train) uses freight cars (also known as wagons or trucks) to transport goods or materials (cargo) essentially any train that is not used for carrying passengers. Much of the world's freight is transported by train, and in the USA the rail system is used more for transporting freight than passengers. Under the right circumstances, transporting freight by train is highly economic, and also more energy efficient than transporting freight by road. Rail freight is most economic when freight is being carried in bulk and over long distances, but is less suited to short distances and small loads. Bulk aggregate movements of a mere twenty miles (32 km) can be cost effective even allowing for trans-shipment costs. These trans-shipment costs dominate in many cases and many modern practices such as container freight are aimed at minimizing these. The main disadvantage of rail freight is its lack of flexibility. For this reason, rail has lost much of the freight business to road competition. Many governments are now trying to encourage more freight onto trains, because of the benefits that it would bring. There are many different types of freight trains, which are used to carry many different kinds of freight, with many different types of wagons. One of the most common types on modern railways are container trains, where containers can be lifted on and off the train by cranes and loaded off or onto trucks or ships. This type of freight train has largely superseded the traditional boxcar (wagon-load) type of freight train, with which the cargo has to be loaded or unloaded manually. In some countries "piggy-back" trains are used: trucks can drive straight onto the train and drive off again when the end destination is reached. A system like this is used through the Channel Tunnel between England and France, and for the trans-Alpine service between France and Italy (this service uses Modalohr road trailer carriers). 'Piggy-back' trains are the fastest growing type of freight trains in the United States, where they are also known as 'trailer on flatcar' or TOFC trains. 'Piggy-back' trains require no special modifications to the vehicles being carried. An alternative type of "inter-modal" vehicle, known as a Roadrailer, is designed to be physically attached to the train. The original trailers were fitted with two sets of wheels: one set flanged, for the trailer to run connected to other such trailers as a rail vehicle in a train; and one set tyred, for use as the semi-trailer of a road vehicle. More modern trailers have only road wheels and are designed to be carried on specially adapted bogies (trucks) when moving on rails. There are also many other types of wagons, such as "low loader" wagons for transporting road vehicles. There are refrigerator cars for transporting foods such as ice cream. There are simple types of open-topped wagons for transportaing minerals and bulk material such as coal, and tankers for transporting liquids and gases. Today however most coal and aggregates are moved in hopper wagons that can be filled and discharged rapidly, to enable efficient handling of the materials. Freight trains are sometimes illegally boarded by passengers who do not wish to pay money, or do not have the money to travel by ordinary means. This is referred to as "hopping" and is considered by some communities to be a viable form of transport. Most hoppers sneak into train yards and stow away in boxcars. More bold hoppers will catch a train "on the fly", that is, as it is moving, leading to occasional fatalities.

History of Cell Phones

The history of cell phones embarks on from the early days of 1920s – a period during which radios were emerging as effective communication devices. The very first usage of radio phones were in taxi/cars using two-way radio communication. Like any other electronic equipment, cell phones evolved over time, and each stage or era was most certainly interesting.

The first official cell phone was used by the Swedish police in 1946. They made it functional by connecting a hand-held phone to the central telephone network. It was very similar to the two-way radio phone that was used in cars/taxis for portable communication.

Rising from this type of communication technology, the evolution of modern cellular phones began. A communication architecture of Hexagonal Cells was created for cell phones by D. H. Ring, of Bell Labs, in 1947. An engineer from Bell Labs discovered cell towers which had the capability to not only transmit but to also receive the signals in three different directions. Before this discovery, the cell phones only worked in two directions and through an antenna.

Pre-Mobile Phones

The electronic components used in cell phones of today’s generation were first developed in the 1960s. During this time, the technology of cell phone was already available. The problem that persisted during that time was the user was restricted to a certain block of areas, which were called cell areas. Cell areas were base stations covering a small land area. If the cell phone user traveled beyond the boundaries of the cell area, the user wouldn’t get signal or receive transmitted messages. There were instances when a call could still be made but the call would be cut once a set range has been reached.

The above limitation of distance was resolved by an engineer at Bell Labs. Amos Edward Joel discovered and developed what he termed as the handoff system. This kind of technology enabled to continue the call from one area to the next and the call would not get dropped. The cell areas for the cell phone users weren’t restricted anymore; the user could freely roam across cell areas without disruption in their calls.

During this time, the technology for cell phones had been developed but it was only in 1971 when there was a request for cellular service. AT&T submitted a request public cellular service to the FCC in 1982. The request was processed almost after a decade. Frequencies of 824 to 894 MHz Band to the AMPS (Advanced Mobile Phone Services) were made possible. Cell phones had analog service since 1982 to 1990. In 1990, AMPS turned digital and went online.

First Generation Cell phones

Motorola was the first company to introduce the first portable cell phone called Motorola DynaTAC 8000X. The FCC approved it for public use after much deliberation and testing of the device. Since then, Motorola has been developing the communication technology of cellular phones. The Motorola DynaTAC took 15 years of development before it was made available to the public market. It was considered to be a lightweight cell phone of about 28 ounces. Its dimensions were 13 x 1.75 x 3.5 inches. It was developed by Dr. Martin Cooper. During those times, Motorola DynaTAC assumed to be high-tech and advance cell phone unit.

Cell phones became popular and received demand from the public during the 1983 to 1989 period. The innovations in communication technology and other networks include the ability of cell phones to handle calls from one area to another area way beyond the venue of the call. In the 1980s, a lot of cell phones were not designed to be hand-held. Formally, “car phone” were installed in cars and this had high demand in the market. Aside from car phones, the earliest models of the first generation cell phones were shaped like tote bags. These were hooked up to the battery of the car through the DC outlet. Other models came in the form of briefcases. This was for large batteries that were needed just in case the user had to make emergency calls.

Second Generation Cell phones

During the 1990s, the technology on which the cell phones worked was called 2G or second generation. This worked on systems like IS-95 or the CDMA, IS-136, TDMA and GSM. The United States and Europe used digital cell phone providers and networks at that time. 2G cell phones were also used to switch the transmissions in the digital circuit which made it easier to make calls. 2G cell phones had a faster network which functions on radio signals. This decreased the chances of calls being dropped thus improvising on call quality. These replaced the analog network frequencies. Eventually, the adaption of modern networks made the analog frequencies obsolete.
The 2G cell phones were smaller, around 100 to 200 grams. These were hand-held and were portable. The advancements happened in cell phones, their batteries, computer chips, etc. Due all these improvements, the cell phone customer base expanded rapidly.

Third Generation Cell phones

The cell phones used nowadays are the third generation phones. 3G was soon launched after 2G. However, the standards that are used in 3G cell phones are different from one model of the cell phone to the next. This essentially depends on the network providers.

3G cell phones have set standards which the network providers need to follow. These cell phones could also message other users via SMS (Short Messaging Service), send emails and access the Internet, stream live videos, stream radio, and use the Wi-Fi.

The History of the Telephone - Alexander Graham Bell

Alexander Graham Bell and Elisha Gray raced to invent the telephone.

Alexander Graham Bell

In the 1870s, two inventors Elisha Gray and Alexander Graham Bell both independently designed devices that could transmit speech electrically (the telephone). Both men rushed their respective designs to the patent office within hours of each other, Alexander Graham Bell patented his telephone first. Elisha Gray and Alexander Graham Bell entered into a famous legal battle over the invention of the telephone, which Bell won.