How VoIp phone systems work

VoIP (Voice over Internet Protocol) phone systems work by sending data via the Internet in tiny packets. This is called packet switching. It works like this:

1. Your voice signal, which is analogue, is converted into digital data. If you have a standard phone, you need an extra piece of hardware to do this called an ATA (Analogue telephone adaptor). If you have an IP phone, it produces a digital signal so you don’t need an adaptor. You can also use your PC and a microphone as a telephone.

2. The sending computer uses software to compress the digital data, much like MP3 files.

3. The data is divided into packets, each one 30 milliseconds long.

4. The packets are sent to a router which decides the best path through the Internet for each packet. They will travel by many different paths. They will arrive at different times and some may even be lost.

5. The receiving computer uses special software to store the packets and put them in the right order. Because the packets are so small, you won’t hear the difference if some are lost.

6. The data is converted back to voice and played through your standard phone, IP phone, or PC headphones.

If you have a wireless VoIP handset, you can make and receive calls anywhere near a wireless hotspot. Some mobile phones are dual-mode. You can use a mobile phone network or wireless VoIP, depending where you are.

Ex. 2. Put the steps in the correct order to make a flowchart showing how this type of VoIP phone system works.

a The packets are sent to a router.

b The digital data is compressed by the sending computer.

с The data is converted back to voice.

d The receiving computer puts the packets back together again.

e The voice signal is converted to digital.

f The digital data is divided into very small packets.

g The router sends each packet through the Internet by the best available path.

1. __e__ 3. _____ 5._____ 7. _____

2. _____ 4. _____ 6. _____

Additional text 1

Ex. 1. Study text A. Try to understand all details. Use a dictionary if necessary:

Text a: The History of Radio

1. Without understanding the inquiries of pure science, we cannot follow the story of radio. It begins perhaps with Joseph Henry, an American physicist, who discovered in 1842 that electrical discharges were oscillating. A gigantic step forward was taken by James Maxwell, a Scottish physicist and one of the great mathematical geniuses of the 19-th century. By purely mathematical reasoning, Maxwell showed that all electrical and magnetic phenomena could be reduced to stresses and motions in a medium, which he called the ether. Today we know that this "electrical medium" does not exist in reality. Yet the concept of an ether helped greatly, and allowed Maxwell to put forward his theory that the velocity of electric waves in air should be equal to that of the velocity of light waves, both being the same kind of waves, merely differing in wave length.

2. In 1878, David Hughes; an American physicist, made another important discovery in the pre-history of radio and its essential components. He-found that a loose contact in a circuit containing a battery and telephone receiver (invented by Bell in 1876) would give rise to sounds in the receiver which corresponded to those that had impinged upon the diaphragm of the mouthpiece.

3. In 1883, George Fitzgerald, an Irish physicist, suggested a method by which electromagnetic waves might be produced by the discharge of a condenser. Next we must turn to Heinrich Hertz, the famous German physicist, who was the first to create, detect and measure electromagnetic waves, and thereby experimentally confirmed Maxwell's theory of "ether" waves. In his experiments he showed that these waves were capable of reflection, refraction, polarization, diffraction and interference.

4. A.S.Popov (1859-1906) was in 1895 a lecturer in physics. He set up a receiver in 1895, and read a paper about it at the Meeting of the Russian Physico-Chemical Society on April 25 (May 7, New Style) 1895. He demonstrated the world's first radio receiver, which he called "an apparatus for the detection and registration of electric oscillations". By means of this equipment, Popov could register electrical disturbances, including atmospheric ones. In March 1896 he gave a further demonstration before the same society. At that meeting the words "Heinrich Hertz" were transmitted by wireless telegraphy in Morse code and similarly received before a distinguished scientific audience, Popov has become the inventor of the radio, May,7 being celebrated each year as "Radio Day" in the Soviet Union.

5. Marconi invented a system of highly successful wireless telegraphy, and inspired and supervised its application. Such is .the story of the many inventors of wireless telegraphy, working with each other's equipment, adding new ideas and new improvements to them. It was a patient, persistent inquiry into natural laws and it was animated by the love of knowledge.

6. During the first years of its development, radio communication was called "wireless telegraphy and telephone". This name was too long for convenience and was later changed to "radio" which comes from the well-known Latin word "radius" — a straight line drawn from the centre of a circle to a point on its circumference. Wireless transmission was named radio transmission, or simply "radio".

7. The term "radio" now means the radiation of waves by transmitting stations, their propagation through space, and reception by receiving stations. The radio technique has become closely associated with many other branches of science and engineering and it is now difficult to limit the word "radio" to any simple definition.

Notes

1. without understanding the inquiries of pure science — незная истоков чистой науки

2. by purely mathematical reasoning — при помощи чисто математических рассуждений

3. does not exist in reality — на самом деле не существует

4. both being the same kind of waves - причем обе являются волнами одного типа

5. distinguished audience — авторитетная аудитория

Ex. 2. Say whether the following statements are true or false:

1. H.Hertz was the first to create electromagnetic waves.

2. A.S.Popov could not register atmospheric disturbances.

3. A.S.Popov is the inventor of the radio.

4. The words "Heinrich Hertz" were transmitted by wireless telegraphy in Morse code.

Ex. 3. Answer the following questions on paragraph I:

1. Who discovered the oscillation of electrical discharges?

2. Does "the ether" exist in reality?

3. What did the concept of an ether help Maxwell in?

Ex. 4. Find information dealing with the discovery made by David Hughes. Relate this information to your partner.

Ex. 5. Which paragraph contains the information directly connected with the invention of radio. Render this information.

Ex. 6. Translate paragraph 5 into Russian/Kazakh.

Ex. 7. Read paragraph 6 and speak about Marconi's contribution to the development of radio.

Ex. 8. Explain the origin of the word "radio".

Ex. 9. Speak about the story of radio using the information from the text.

Additional text 2

Ex. 1. Read the title of the following text. Can you guess what the text might be about?

Ex. 2. Study text B. Try to understand all details. Use a dictionary if necessary: