Прочитайте текст и выберите утверждение соответствующее содержанию текста In the early days of the t...: ответ на тест 781530 - Английский язык

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In the early days of the telegraph and the telephone, men observed that signals sometimes jumped across the space between wires running next to each other, so that messages sent to one person went to another. They realized that electricity could pass through the air as well as along a wire. Just as sound travels through the air in waves, so electricity travels through the air in what we call radio waves. A. S. Popov, a Russian inventor, had the idea of sending messages by radio waves, or "by wireless". He constructed a coherer detector for the study of lightning discharges and his receiver was described in 1895.

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In the early days of the telegraph and the telephone, men observed that signals sometimes jumped across the space between wires running next to each other, so that messages sent to one person went to another. They realized that electricity could pass through the air as well as along a wire. Just as sound travels through the air in waves, so electricity travels through the air in what we call radio waves. A. S. Popov, a Russian inventor, had the idea of sending messages by radio waves, or "by wireless". He constructed a coherer detector for the study of lightning discharges and his receiver was described in 1895.

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Radio was invented in Russia. The world's first receiver was constructed in 1895 by the great Russian scientist Alexander Popov. There were no transmitters then, therefore his receiver could only pick up signals produced by lightning discharges during a thunderstorm. A. Popov demonstrated a device called a "storm indicator" at a meeting of the Russian Physico-Chemical Society in St. Petersburg on May 7, 1895. This day is marked now as Radio Day. Soon Alexander Popov found a way of transmitting Morse code signals. In 1897 he sent the world's first wireless telegram over a distance of 600 m and four years later the range of transmission was increased to 150 km. Nowadays radio communication has no limits.

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The first television invention that had practical consequences was the “electrical telescope”, patented by Paul Nipkow in 1884. At the heart of his camera was the now famous Nipkow disk. It had 24 holes equally spaced along a spiral near the periphery of the disk. The image to be transmitted was focussed on a small region at the disk’s periphery, and the disk was made to spin at 600 revolutions per minute. As the disk rotated, the sequence of holes scanned the image in a straight line. A lens behind the image region collected the sequential light samples and focussed them on a single selenium cell. The cell would then produce a succession of currents, each proportional to the intensity of the light on a different element of the image.

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Zworykin’s most critical invention was the first iconoscope camera tube, which he patented in 1923. The key to its success was the fact that its silvered-mica photocathodes stored the charges induced by the image that was focussed on them until the scanning electron beam simultaneously neutralized the charges and modulated itself.
A year after he invented the iconoscope, Zworykin invented the kinescope - a TV picture tube - thus becoming responsible for both the key transmitting and receiving elements of electronic television.

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The technical problems of colour television have been solved long ago - a German patent for the transmission of images in colour was taken out by the physicist, Otto von Bronk, as far back as 1902 - but the high cost of the equipment, especially receivers, has held up its general introduction. In America, television programmes in colour have been transmitted since the early 1950’s to a limited number of viewers who can afford the extra cost, and an experimental service began in Britain in 1955. Japan started its regular colour service in the autumn of 1960: a year later there were already 15,000 receiving sets in operation, although the price of a colour set was still eight times as much as that of a black-and-white receiver. Then the Soviet Union, too, has introduced a colour television service.