Television, radio, videos etc. have been widely replaced by the Internet and much more complex devices. Today you can listen to several radio stations and watch TV over the Internet. The television set itself has also become an interactive system and is already not used only for watching purposes. Video is steadily being replaced by DVD and you can buy almost any movie through the Internet and you do get some legal mp3-sites.

The Television

No moment can be singled out as the moment when TV was invented and it's even harder to say who's contribution was of the most significance. It started in the 1880's when problems regarding the transmission of pictures was seen as needed to be solved but the term television was not used until the beginning of the 20th century. Then the goal of inventors was not entertainment and bringing news but they wanted to make telecommunication more advanced than the telephone by using pictures as well as sound. Developers faced many problems but one main problem was that a transducer was needed to turn light to electricity. Eventually they found that the element selenium can do just this. Another problem was scanning, breaking a moving image up into smaller transmittable parts.

John Logie Baird is often seen as the inventor of the TV but his mechanical system was soon replaced by electric systems much like we know today. The development of the cathode-ray tube was the centre of developing the electronic television. The cathode-ray tube is simply a vacuum tube with a beam of high-energy electrons focusing in a fluorescent screen to give light. In the 1920's the development of the TV really began to pick up speed. There were great profits to be made out of the making of communication goods after the success of radio just after 1918. Now people began to think of the TV as a broadcasting medium rather than another form of telecommunications and people started to pursue new relaxing activities inside the home. Other important developments were made by Vladimir K. Zworykin. He visualised a camera tube that used electrons to scan over a surface charged by exposing it to light but couldn't produce a working prototype. Later he was commissioned by RCA to extend European developments in cathode-ray technology. In 1929 he developed a prototype of modern picture tubes and called it the kinescope. His team developed the iconoscope in 1931, the camera tube he visualised eight years before.

The light of an image and the sounds are converted into an electronic signal by a video camera and can then be transferred to video tape. The image is converted into electricity by focusing the light reflected by the image onto a light sensitive surface. An electron beam scans over the image and changes each light value into the equivalent electrical charge.

 Each signal consists of the image, sound and a synchronising pulse. The pulse makes sure that the image and sounds from the camera or video tape at the transmission end correspond with those of the TV set. A device in the TV set amplifies these elements and separate them. The sound is changed back into an audio signal and amplified into the loudspeaker. A different circuit picks up the synchronising pulse. The picture signal is diverted to the picture tube. There are three electron guns at the back of the funnel-shaped vacuum tube. They fire electron beams at the florescent coated screen and light it up. The electron gun is a metal cylinder and it fires streams of electrons at the back of the screen. An anode (positive element) pulls all the negative electrons away from the cathode. The picture signal determines how many electrons should pass through to the screen. Every beam respond to one of the three primary colours, red, blue and green. All the colours on the TV screen can be produced by combining these three colours in different ways.

The synchronising signal also controls the movement of a scanning spot, which moves in a horizontal line. It activates electronic dots formed by chemicals called phosphors at the back of the screen. The scanning takes place at a great speed. The image signal determines how bright each picture element should be and which combination of red, blue and green and how strong or pastel it should be. There are over a million phosphor dots on a colour TV screen and they are arranged in small triangles of red, green and blue. The electron beams only respond to the dots of their colour.

The control centre of any TV station controls which pictures are to be broadcasted. The signal is attached to a certain pattern of waves on a particular wavelength or frequency and broadcasted from the broadcast station's transmission antenna. To be able to carry audio as well as visual signals TV needs a far wider bandwidth than radio. The TV signal and carrier waves are relayed via stations. Your receiving antenna picks up the signals and you can decide on which channel's frequency you want the TV to be.

A relatively new development is HDTV (High Definition TV). Resolutions of 1 125 to 1 250 lines are possible which opens the door for displaying on a much larger screen without losing picture quality. HDTV systems are still very expensive but may eventually become more widely available.

Makers of consumer goods are concentrating far more on new high-technology entertainment services. This way of thinking brought about three technologies that changed the TV market, cable, satellite and video. Cable was originally developed to get better reception in areas where the airwaves were somehow blocked. Now pictures were fed directly to receivers by coaxial cable instead of antennas picking up the signals. Cable also involves bringing many more channels to the public but at extra cost.

Digital TV is a multichannel system initiated by cable and satellite. By converting the TV signals into binary code many signals can be compressed into relatively small electronic space. This brings hundreds of channels to viewers. Not all the channels are TV channels but there are also radio stations and games.