You probably call it a TV, but the true word for that colorful, busy rectangle that brings you your favorite programs is a television. Tele is Greek for distant and the Latin word vision means to see. So in fact, you are seeing something that is or was happening at a distance from you.
A Little History
We have all become fairly used to having television in our homes, our schools, even in our restaurants. And it is even common in this century for us to have more than one television in our homes. But there were no televisions until around the year 1927. Many people are credited with helping to invent the television. In truth, it seems to be a difficult question to pin down who actually invented the TV. But a young Idaho farm boy was able to demonstrate electronic television on September 7, 1927 in San Francisco when he transmitted a single line using a vacuum tube. Philo T. Farnsworth had gotten the idea of creating television pictures by dividing the picture into rows- much the way he created rows of turned over soil while plowing the fields on the farm. For additional information about Mr. Farnsworth and his work visit this website which tells about his history. He was a very smart man with a lot of knowledge about other things besides television.
The first electronic television that Mr. Farnsworth had created was very primitive. Pictures were originally very small and orange in color. Images were often blurry and difficult to see. The creation of new and better ways to send images has improved and changed many times since then. For a view of early American televisions (or television sets as they were often called) head to Television History.
The television had great potential to show people news events happening around the world and music and sports programs that they could only dream of seeing. In the early days of American television, NBC (National Broadcasting Company) and CBS (Columbia Broadcasting System) were the two primary broadcasting companies. Both are still in operation today. By 1943 the American Broadcasting Company (ABC) also entered into the television industry. In time, news and sports welcomed programs of comedy, musical talent, game shows, and other programs which had previously been a part of radio programming. Movies also came to be a very popular program. All of the television programs were shown in black and white and shot with a single camera. Networks only showed programs during certain hours of the day and closed down late at night.
In the 1950s and 60s many families were still unable to afford a television in their homes. Few families owned more than one television and they were considered a luxury item. Color television was introduced in 1964 but people could not see color from their black and white televisions. So people who wanted to view color television were forced to go out and buy another TV or live with the black and white.
In 1967 PBS (Public Broadcasting System) was born. PBS still brings you programs like Science Trek and Sesame Street along with many, many others. Programs from CBS, NBC, ABC and PBS were viewed by most Americans. But, even in the 1960s some parts of the country were unable to view television because they lived in areas not able to get service. Cable television was the new way to get service to homes and businesses who had not had access before. Satellite television joined them in the 1980s.
Now today we have access to hundreds of networks and thousands of programs to watch 24/7. In addition, video games, videos, the internet, video-conferencing and much more can be seen from the comfort of your big screen TV. And if that's not enough for you, there's also television on your phone, your tablet, or your computer so that you won't have to ever miss an episode of Science Trek!!
Television Needs Radio
In order to understand television, we need to understand radio waves. Radio waves are part of what is known as the electromagnetic spectrum. The electromagnetic spectrum includes all light and sound waves- those that can be seen or heard and those that cannot be seen or heard like x-rays, microwaves and many others To understand more about the electromagnetic spectrum, you might want visit to Science Trek's sites on Light & Color and Sound.
Radio waves are the longest waves of the electromagnetic spectrum. They are too long for our ears to hear them without the use of the workings of a radio. When you tune a radio to a specific station, you are zeroing in on a given wavelength. Your radio converts the waves to mechanical vibrations and you hear music, the announcer, and drum beats. Most of us listen to FM stations, but there is also a set of waves where the AM stations exist. A television receives radio waves in a space in between FM and AM radio.
The broadcasting company or television station sends out signals using these waves. This signal has all of the images, music, dialogue, and data necessary for you to watch the program you have decided to watch. Each channel runs at a slightly different wavelength which carries that channel's programs.
If your television has an antenna, then the antenna picks up the signal that was sent out from the broadcast company or the television station. This is sometimes known as sending it out over the air, even though air has nothing to do with it. In order for the antenna to work, the signal must be in direct line from the source to your TV. If mountains or canyons- or the curve of the earth - get in the way, no TV.
In the early days of TV everyone had an antenna. Sometimes the antenna sat on top of the television. These were often affectionately called “rabbit ear” antennas. Sometimes the antenna was mounted to the roof or hidden inside the attic.
Cable companies get around this direct line problem by sending the signal directly to your television. Cable companies have their own antennas which they use to collect the signal and then they send it to your television over a wire- or cable.
Satellite television can transmit further distances, around mountains and over the curve of the earth because they send the signal from the source to a satellite orbiting the earth and then the satellite sends it back to the earth again. The signal is then gathered in by a special antenna known as a satellite dish. Original satellite dishes were huge and took up a large part of the user's back yard. Over time they have been made smaller. If you have one, it is a little bigger than a dinner plate and attached to the side of your house. Large ones are still used for broadcasting companies and have other uses in science and business.
How The Station Sends the Signal
A station's program is often filmed or videotaped. When this is done, the result is a series of still pictures, each with a slight change in the action. When played back, our brain pieces these images together to form movement. It is almost like an optical illusion. We actually see each single still image, but it seems to us as fluid movement.
Sound is added to include dialogue, conversations, sound effects and music. Sometimes the sound is part of the original videotape- like when the newsman reads the news. But in movies, sound can be added in layers. There is the conversation layer. Then sound effect people add the sirens and the squealing tires. Special artists known as Foley artists create the extra sounds like people walking, closing doors, and even special effect sounds like aliens landing or laser guns being fired.
Then, all of this- video and sound - is sent out using a transmitter to generate the radio waves. Transmitters of varying sizes are used for all sorts of equipment, from remote control cars to garage door openers. Small transmitters are sometimes attached to wild animals to track their migration habits. Transmitters for broadcasting television are large tower-like equipment used by television stations and broadcasting networks. Sometimes mobile transmitters are attached to the top of a van or truck for going out to the site of a news event. These look a lot like an oversized satellite dish on a van.
How the Television Works
Televisions have changed over time. Early televisions used cathode ray tubes or CRTs. They are not used much anymore, but a few are still around. You would recognize them by their large and bulky shape. The CRT, which is somewhat funnel shaped, sends electrons through a vacuum to the backside of the screen. The backside of the screen is coated in phosphor which glows when the beam of electrons strikes it. The beam is steered across the screen by steering coils which are made of coiled up copper wire. They create magnetic fields which attract the beam across the screen in rows- similar to Farnsworth's farming observation. The beam moves back and forth in what is referred to as a raster scan pattern. The intensity of the beam changes as it moves across the screen to create rows of dots using variations of white to gray to black, depending upon the beam's output. These dots are known as pixels. The beam redraws the image or refreshes 60 times per second. Your brain is able to translate these rows of shading into recognizable images.
Special signals are sent by the broadcasting station to tell the television when to move the beam back and forth across the screen, how intense to make the beam and when to repeat this process.
In a color television, there are three beams of electrons which are attracted to dots of phosphor which glow red, green or blue when struck by the electron beam. These dots, or pixels, are very small and are arranged in a grouping of the three colors, repeated over and over across the screen. The colors we see as we watch a television image, are combinations of the three colors or the absence of any color to produce black. Again, your brain is able to translate the various combinations into an image. Magazine and newspaper images use the same concept. Look at one up close and you will be able to see the pixels.
Flat screen or plasma televisions, which are more common today, do not use CRT technology. Instead they use thousands of tiny cells filled with xenon and neon gases that light up in red, green and blue when pulses of electrical current pass through them. This avoids the large tube in the back of the television, making it possible to hang them on the wall and to produce larger and larger screens.
Some televisions use what is known as an LCD (liquid crystal display) screen. It is also flat and very similar to a plasma screen but instead of using plasma gases they have liquid crystals which turn special cells on or off as needed to produce an image. These cells contain the three colors - red, blue, and green.
It Takes A Lot of People
A television program is not a simple thing to put together. It takes a number of people to do all of the jobs necessary to provide television programs to your television. And different programs need different people. The news needs an entirely different staff than your favorite comedy program. Here are just a few of the jobs that might be necessary to run a television program.
Director: tells the actors where to stand, when to move.
Actors: the people you see acting out the story.
Camera operator: videotapes the action.
Sound: makes sure the sound quality is good.
Set: the major parts like furniture, walls, windows.
Lighting: makes sure the lights shine in the right places.
Costumes: provides the clothing, repairs the costumes.
Makeup: you know that actor isn't really a monster, but he sure looks like one!
Animal handlers: does the show have a dog in it?
Props: makes sure that the extra stuff is there like pens, telephones, books, mail, dishes, etc.
These are not all of the jobs required, either. Special effects people make the giant robot work and the rockets take off, people feed the crew and teach the child actors. Sometimes people must talk with accents, so there are people to teach language and sometimes to teach dancing moves – whew!!! It's exhausting just to think about it all. Don't turn off the movie after the last scene. Watch the credits at the end – you will get a better idea how many people must work towards that final product you watched. The end of the news, the end of game shows, sports programs, reality shows, movies and the end of Science Trek all have credits to tell you who is responsible for getting that program to your TV.
Television shows use still images that change ever so slightly over and over in a series to simulate movement. Our brain is what makes us think it is in motion.
The first remote control was invented in 1955 – called the Flash-Matic.
Large televisions could not function using a CRT – the tube out the back for the beam would need to be gigantic and would take up almost as much space behind the screen as the screen was large.
The first legal television commercial was for the company Bulova which makes watches and jewelry.
Televisions are measured from the top corner to the opposite, bottom corner for size identification.
Satellites used for sending television signals are in what is known as a geosynchronous orbit. This means that while it is orbiting the earth, it is keeping speed with the turning of the earth. This allows it to stay over a given spot above the surface.