Referat Voices Across the Earth - Transmitting Voices

Voices

Across the Earth

Table of Contents:

Voices Across the Earth

1. Introduction

2. Main Part

The First Electronic Communication

2.2 Transmitting Voices

2.3 Radio Waves

2.4 Recording Sound

2.5 In the Modern World

3. Appendix

4. Handout

5. Notes

6.Glossary

Voices Across the Earth

1. Introduction:

First I want to say that communication links between people have always been important.

Today we live in the Communications Age and we owe this to inventors in the last century. Now I want to tell you something about these inventors.

In ancient times, bonfires on hilltops were used to signalling danger. The North American Indians used smoke signals and the Romans flashed messages with mirrors turned to catch the sun. Sending messages in this way worked well in certain circumstances. If the messages were complicated, a code had to be used, which had to be understood by everyone. The only other way of communicating was to send a written message, which took time if the people involved lived any distance apart.

2. Main Part:

2.1 The First Electronic Communication:

The invention of electric power revealed many possibilities for communication. The first telegraph was patented by a British scientist, Sir Charles Wheatstone and an Indian Army Officer, Sir William Cooke, in 1837. It used needles which pointed at different letters in response to electric currents. Some codes were created to communicate with this new invention. In the following picture we can see the different codes.

The Semaphore code, developed in 1794, used a system of moving arms worked by ropes to create symbols for each letter. Samuel Morse's code could be transmitted along a wire using a key. This code is shown as dots and dashes. The code could also be transmitted with flashing lights. The Five-unit code was developed from the Morse code for using with a teleprinter, an instrument for typing telegraphs to be sent along telephone wires.

Morse established the first telegraph line between Washington and Baltimore in 1844. By the 1860's telegraph wires connected the East and West Coast of the United States and there was a cable across the Atlantic to Europe.

2.2 Transmitting Voices

Communication by telegraph was quicker than sending a letter, but slower than speaking to the person directly. If coded messages could be sent along electric wires, could the human voice also be transmitted?

Alexander Graham Bell gave us the answer. He knew that sounds make vibrations on the eardrum which the brain translates to make sense of them. His idea was to make a transmitter with a disc which would vibrate when struck by sound waves, in the same way as the eardrum. Sound vibrations from the transmitter would pass along a wire to a receiver which would also have a vibration disc. This receiver would convert the sound vibrations back into words. On March 6, 1876, the first words were transmitted. The telephone had been invented.

Now, in theory, it was possible to communicate by telephone with anywhere in the world. But one problem was still how to link up telephone lines so that people could ring up anyone they liked.

The answer was a telephone exchange, where lines from different telephone subscribers could be plugged into a switchboard to connect them to each other.

By 1885, there were 140.000 subscribers and 800 telephone exchanges. The first telephone exchanges were manual, which meant that operators sat in the exchange and plugged the lines into a switchboard by hand to connect calls. Today the calls are connected by computers.

2.3 Radio Waves

In the middle of the nineteenth century, scientists began to examine the idea of transmitting sounds without wires. The first man to introduce the idea of electromagnetic waves was the British scientist, James Clerk Maxwell, who demonstrated that light is an electromagnetic wave and suggested the idea of radio waves. In 1888, the German scientist, Heinrich Hertz, produced and detected radio waves with a simple transmitter.

When Guglielmo Marconi, an Italien electronic engineer, read a newspaper report about electromagnetic waves in 1894, he resolved to find out if these "wireless" waves could be used to transmit sound. To make the receiver more sensitive to the signals, he connected a long vertical wire with the receiver. Marconi worked on this invention until he managed to send a signal from his house to a field two kilometres away.

Electromagnetic waves such as light and radio waves travel faster than sound. To transmit sound by radio waves, a microphone in a transmitter converts them into electrical signals. The signals pass to an aerial in the transmitter and spread out as radio waves. The aerial on the receiver picks up the waves and a loudspeaker turns them back into sound.

In 1899, Marconi transmitted a message about fifty kilometres across the English Channel and in 1901 he made the first radio link across the Atlantic. In 1920, the Marconi Company broadcast the first British radio programme.

2.4 Recording Sound

Another new idea was the concept of storing sounds on a solid material so that they could be played over and over again. One of the greatest inventors, Thomas Alva Edison, invented the phonograph for recording and playing sound. He got the idea from the telephone, which had recently been invented. He constructed a recording machine and shouted the world "HELLO" into it. The sound that came back to him was an indistinct but definite "HELLO".

Edison's first recording was the nursery rhyme "Mary had a little lamb". Edison's invention brought him worldwide fame, but his phonograph was very basic. The sound quality was not good and the cylinders did not last long. Edison was more interested in thinking up new ideas than in perfecting his inventions and it was left to others to improve on the phonograph.

After Emile Berliner had found a way to make records in 1887, he went on to design a machine for playing them: the "gramophone". The early gramophone had a large horn for making the record sound louder. The machine had to be wound up with a handle to make the turntable revolve.

2.5 In the Modern World

Today, all these methods of communication have moved forward in ways which their inventors could never have imagined. People can now listen to the music of a complete orchestra, with the sound of each instrument faithfully reproduced.

Equipment which produces high quality and accurate sound reproducing is known as high-fidelity or "hi-fi" equipment.

The latest method of reproducing music is digital recording, which is stored as a digital code and is translated into sound by a computerized player.

The compact disc is the best-known form of digital sound recording. It produces the finest-quality sound available at the moment.

The telephone can link people on opposite sides of the world in seconds, people have telephones in their cars and a telephone which shows a picture of the caller and recipent on a small screen is now becoming available. Documents are fed into a fax machine which turns the text and pictures into electronic signals. The signals are sent along the telephone wires and a fax reciever at the other end turns them back into exact copies of the documents sent.

Communications satellites have made it possible to link up distant corners of the world and even to communicate with craft in space.

One day in the future we may be able to use Marconi's idea to communicate with extraterrestrial civilizations.

3. Appendix:

The communication codes:

4. Handout:

Contents:

In ancient times:

Bonfires on hilltops were used to signalling danger - North American Indians used

smoke signals - Romans flashed messages with mirrors

In the electronic age:

first telegraph - British scientist, Sir Charles Wheatstone - Codes were created to

communicate with this invention

first telephone - Alexander Graham Bell - on March 6, 1876, the first words were

transmitted

first radio -      Guglielmo Marconi - 1899, Marconi transmitted a message about

fifty kilometres - In 1920, the Marconi Company broadcast the first British radio

programme.

Recording Sound:

first recording - Thomas Alva Edison - 1877, Edison invented the phonograph

In the modern world:

communication today: TV, Handy, Inet, Cserve,

recording today: CD, MD, DCC, MC, (LP),

Notes:

6. Glossary: