2 The ElectromagnetIn 1825, British inventor William Sturgeon ( ) revealed an invention that laid the foundations for a large scale evolution in electronic communications: the electromagnet.Sturgeon displayed the power of the electromagnet by lifting nine pounds with a seven-ounce piece of iron wrapped with wires through which the current of a single cell battery was sent.NOTE: 1825 William Sturgeon invented the electromagnet
3 The TelegraphIn 1830, an American, Joseph Henry ( ), demonstrated the potential of William Sturgeon's electromagnet for long distance communication by sending an electronic current over one mile of wire to activate an electromagnet which caused a bell to strike.
4 However, it was Samuel Morse ( ) that successfully exploited the electromagnet and bettered Joseph Henry's invention. Morse invented a telegraph system that was a practical and commercial success.In 1838 He used pulses of current to deflect an electromagnet, which moved a marker to produce written codes on a strip of paper - the invention of Morse Code. The following year, the device was modified to emboss the paper with dots and dashes.NOTE: Samuel Morse creates the telegraph and the “dot and dash” Morse Code.
5 The first machine recording voice was called phonograph The first machine recording voice was called phonograph. It was developed as a result of Thomas Edison's work on two other inventions: the telegraph and the telephone. Edison was working on a machine that would transcribe telegraphic messages on paper tape, which could later be sent over the telegraph repeatedly.
6 This development led Edison to speculate that a telephone message could also be recorded in a similar fashion. He began experimenting with the diaphragm of a telephone receiver by attaching a needle to it. He reasoned that the needle could prick paper tape to record a message. In 1877 his experiments led him to try a stylus on a tinfoil cylinder, which, to his great surprise, played back the short message he recorded, "Mary had a little lamb."
8 Edison did no further work on the phonograph for a while, concentrating instead on the light bulb. And so others moved forward to improve on his invention, including Chichester A. Bell and Charles Sumner Tainter, who developed a wax cylinder for the phonograph. In 1887 Edison resumed work on his phonograph and used wax cylinders too. These early cylinders had two significant problems.The short length of the cylinders, only 2 minutes.There was that no mass method of duplicating cylinders.
9 In 1895 Emile Berliner revolutionized the future of recorded sound. Berliner's gramophone differed its contemporaries in that it used a flat shellac disc to record sound rather then the cylinder proposed by Edison. The disc permitted mass duplication and playing time was 4 minutes.
11 Fast forward The first disc recorded by electrical equipment :1920 Gramophones turned by electricity (instead spring motors) :1925.First “long playing” discs (knows as LP's) :19041931 standard speed 33.3 r.p.m.The shellac discs, which were Brittle, were replaced in by plastic ones.micro-grove discs :1948.
13 Why Different Speeds?Emil Berliner determined roughly how fast old disc records should spin.He avoided Edison's need for a stylus made from precious jewels by using points which could be made from steel sewing needles and pins.The size of the stylus effectively determined the size of the grooves in a record and the recordable frequency range limited by this groove size determined a speed between 70 and 90 rpm