Sunday, September 26, 2010
Monday, February 15, 2010
Telegram
The Invention of the Telegraph(Samuel Morse):
The telegraph is defined as any system that allows the transmission of encoded information by signal across a distance. The meaning of "telegraph" comes from Greek words: tele = far and graphein = write. While telegraph systems have used a variety of signaling methods and devices, the term is most often applied to the electrical telegraph development in the 19th century. The earliest forms of telegraphy were probably smoke, fire or drum signals. In the late 18th century optical telegraphs were invented by Claude Chappe in France and George Murray in England – the semaphore, based on visible transmission encoded by different positions of pivoted arms located on high towers, but this slow and ineffective system couldn't work at night. Rapid development of the electrical telegraph was based on Hans Christian Oersted’s discovery in 1819 that a wire carrying a current was able to deflect a magnetized compass needle. The Cooke and Wheatstone five needle telegraph of 1837 utilized this phenomenon. This apparatus, which is generally regarded as the first functional electric telegraph, was widely used in Great Britain for railroad signaling. The needle telegraph, even after improvement, required two or more lines to form a complete circuit. It was also relatively slow and the design of the transmitting and receiving instruments was complex. Something simple and efficient was needed. In 1825, British inventor William Sturgeon, exhibited the electromagnet for the first time. Sturgeon displayed its power by lifting nine pounds with a piece of iron wrapped with wires (electromagnet) through which the current of a cell battery was sent. In 1830, an American inventor, Joseph Henry, demonstrated the potential of Sturgeon's device for long distance communication by sending an electronic current over one mile of wire to activate an electromagnet which caused a bell to strike. Thus the electric telegraph was born. Samuel F.B. Morse successfully exploited Henry's invention commercially. Together with his partner Alfred Vail, Morse developed in 1838 the simple operator key, which when depressed completed an electric circuit and sent a signal to a distant receiver which was an electromagnet that moved a marker that embossed a series of dots and dashes (the Morse Code) on a paper roll (patent No.1647). About 1856 a sounding key was developed that enabled operators to hear the message clicks and write or type it directly down in plain language. Telegraph systems quickly spread across Europe and the United States. With the growing telegraph traffic many improvements followed. Like the duplex circuit, in Germany, that made it possible for messages to travel simultaneously in opposite directions on the same line. Thomas Edison devised a quadruplex in 1874 that enabled four messages to travel at once. The most revolutionary invention was that of Jean-Maurice-Emile Baudot, his time division multiplex invented in 1872. Further qualitative improvements were made by Marconi, Tesla, Lodge, Edison, and others by the introduction of the wireless telegraph (radio).
Device of telegram:
A simple telegraph is a really simple electrical circuit. At the transmission station we have a Morse key which can be a homemade switch from some flexible electricity conducting metal strip like tin or a Radio Shack switch. When pushed down it closes the electrical circuit through the telegraph line and operates a homemade electromagnet or relay at the receiving station (sounder). The electromagnet activates a switch which activates a bulb / LED or buzzer / bell according to the Morse key rhythm (“dash” dot”).
Time line of telegram
Since the beginning of time, man has experimented with ways of sending information over great distances. Smoke signals, fire towers, flags and talking drums were all used as early systems of communication. It was the development of electricity that enabled the modern telegraph to come into being.
1727 – In London, Stephen Gray transmits electricity 700 feet through a wire suspended in the air by silk threads
1753 – First practical suggestion for an electrical telegraph is made in Scotland
1774 – First functioning telegraph is demonstrated in Geneva, Switzerland
1793 – The word 'telegramme' is used with reference to sending and receiving messages by means of an optical communication system
1832 – Samuel Finley Breese Morse propounds the theory that information can be transmitted by opening and closing an electrical circuit
1836 – Morse builds his first functional telegraph instrument
1844 – Morse sends the first public telegraph message “What Hath God Wrought”
1851 – Over 50 separate telegraph companies in the United States
1852 – The word “Telegram” is first used in the Albany Evening Journal
1854 – Military telegraph is used for the first time during the Crimean War
1858 – Telegraph systems of Europe and North America are connected
1895 – Western Union transmitting 58 million messages annually
1920’s – Telegraphers stationed at boxing matches and baseball games
1930’s – Singing telegrams introduced in addition to Santagrams, Bunneygrams and Kiddiegrams
1940’s – Postal Telegraph and Western Union merge and telegram service suspended in the UK due to War
2006 – Western Union delivers its last telegram
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Monday, February 8, 2010
Horse Power
Ask a car enthusiast and most of the time you'll get a blank look, a shrug of the shoulders and maybe a guess along t
he lines of "What ahorse can do!"
Horsepower is defined as work done over time. The exact definition of one horsepower is 33,000 lb.ft./minute. Put another way, if you were to lift 33,000 pounds one foot over a period of one minute, you would have been working at the rate of one horsepower. In this case, you'd have expended one horsepower-minute of energy.
Even more interesting is how the definition came to be. It was originated by James Watt, (1736-1819) the inventor of the steam engine and the man whose name has been immortalized by the definition of Watt as a unit of power. The next time you complain about the landlord using only 20 watt light bulbs in the hall, you are honoring the same man.
To help sell his steam engines, Watt needed a way of rating their capabilities. The engines were replacing horses, the usual source of industrial power of the day. The typical horse, attached to a mill that grinded corn or cut wood, walked a 24 foot diameter (about 75.4 feet circumference) circle. Watt calculated that the horse pulled with a force of 180 pounds, although how he came up with the figure is not known. Watt observed that a horse typically made 144 trips around the circle in an hour, or about 2.4 per minute. This meant that the horse traveled at a speed of 180.96 feet per minute. Watt rounded off the speed to 181 feet per minute and multiplied that by the 180 pounds of force the horse pulled (181 x 180) and came up with 32,580 ft.-lbs./minute. That was rounded off to 33,000 ft.-lbs./minute, the figure we use today.
Put into perspective, a healthy human can sustain about 0.1 horsepower. Most observers familiar with horses and their capabilities estimate that Watt was a bit optimistic; few horses could maintain that effort for long.
Although the standard for rating horsepower has been available for over 200 years, clever car manufacturers have found ways to change the ratings of their engines to suit their needs. During the famous horsepower wars of the 1960s, manufacturers could get higher figures by testing without auxiliary items such as alternators or even water pumps. High ratings backfired when insurance companies noticed them and started to charge more for what they saw as a higher risk. Manufacturers sometimes responded by listing lower horsepower figures, forcing enthusiasts to look at the magazine test reports to determine what was going on. In the early seventies the SAE (Society of Automotive Engineers) stepped in with standardized test procedures and the fiqures were more consistent.
Between 1922 and 1947, the Royal Automobile Club used a horsepower rating that was the basis for an automobile tax. The horsepower of an engine was determined by multiplying the square of the cylinder diameter in inches by the number of cylinders and then dividing that figure by 2.5. Using this dubious method, What we know of as a 385 horsepower motor found in the 2001 Z06 Corvette would be rated at only 48.67 hp!
There is a metric horsepower rating, although it is rarely used. The two methods are close, with one SAE horsepower equal to 1.0138697 metric horsepower.
One mechanical horsepower also equals 745.699 watts or .746 kW (kilowatts) of electrical horsepower. This means that if you really want to confuse people, you could complain about the 0.0268 horsepower light bulb your landlord has in the hallway as opposed to the mundane 20 watt measurement.
So friends better be clear about the horses before you talk about your machines......
