KHOWLEDGE ZONE

You probably have a favorite television show. Maybe you have more than one favorite TV show. Did you ever wonder where your favorite shows come from? Did you ever wonder how they get to the TV set in your home?

WHERE DO TV SHOWS COME FROM?

Some TV shows are made in TV studios. Some of these shows are broadcast live—that is, as they are being made. Some shows are taped in the studio. The tape gets played on TV later on.

Other TV shows are made outside of studios. Baseball and football games and other sports events come from stadiums. Some parts of news programs are broadcast “on the scene.” TV reporters go to the scenes of accidents, floods, and fires and describe what is happening.

Shows in studios are made on sets. Sets for plays or soap operas can look like living rooms or kitchens. Sets for talk shows might have a desk for the host and chairs for the guests. Bright lights shine down on the sets.

HOW ARE TV PICTURES MADE?

A TV picture starts with a TV camera. Some TV cameras are big and some are small. The cameras in TV studios are big. Camera operators roll the big cameras around on wheels. There are usually several big cameras in a TV studio. Cameras used outside a TV studio are smaller. TV camera crews take the smaller cameras to news and sports events.

Some cameras send out live pictures to your TV set. Some cameras make videotapes that get played later on a television program.

All TV cameras need electricity to work. A camera operator points the camera at a scene. The camera picks up light from the scene. It changes this light into an electric signal called the video signal. A microphone changes the sound of people talking or music playing into an electric signal called the audio signal.

TV cameras do not snap pictures the way an ordinary camera does. Parts inside a TV camera scan, or sweep over, the scene and trace a series of thin, horizontal lines, one below the other. A TV camera scans a whole scene much faster than you can blink. Lines from the scans go together to make a picture.

THE TV CONTROL ROOM

The pictures and sound from the TV cameras and microphones go to a control room. Every television station has one or more control rooms. TV cameras in a studio can send live pictures to the control room. The control room is full of dials, switches, and small TV screens. There are screens that show pictures from each TV camera in the studio.

Producers and directors work in the control room. They make sure that the best pictures with the best views go to your TV screen at home.

People who work in control rooms also use taped pictures to make programs. They use computers to put together the best taped scenes.

HOW DOES THE SHOW GET TO YOUR HOME?

The picture and sound signals go from the control room to a transmitter. The transmitter makes the signals stronger and sends them to a transmitting antenna. This antenna is very tall. It changes the electric signals into invisible television signals that go through the air. The television signals go out from the antenna in all directions.

TV signals can get to the TV set at your home in several ways. They can go through the air to an antenna on your roof. The antenna picks up the signals and sends them through wires to your TV set. The signals could go to a cable TV company. The company sends the signals through a cable to your home. The TV signals could come right to your house from a satellite circling high above Earth. A satellite dish outside your home can pick up the TV signals and send them over wires to your TV set indoors.

HOW DOES YOUR TV SET WORK?

Your TV set changes the television signals back into pictures and sound. Your set picks up the thin lines that the TV camera scanned. Your set uses parts called electron guns to “paint” a picture on the TV screen one thin line at a time. The lines get painted from top to bottom.

A color TV set uses three electron guns to beam out three colors—red, green, and blue. These three colors make all the colors you see on your TV screen. The beams scan fast enough to paint a picture on your screen 30 times a second.

OTHER WAYS TO USE TELEVISION

Television can do many things. TV cameras can be sent to places that are difficult or dangerous for people. They can travel to outer space. Spacecraft carry TV cameras to other planets. The cameras send back pictures that let us see what other planets look like.

TV cameras on robot submarines can go deep down in the sea. Doctors use tiny TV cameras to see inside the human body.

WHEN WAS TV INVENTED?

Inventors made the first TV pictures in the 1920s. Television stations started broadcasting the first regular TV shows in the 1940s. The first TV sets had small screens. The first TV sets showed black-and-white pictures.

Television sets have gotten better and better. Most TVs sold today show color pictures. TV screens have gotten bigger and bigger. TV sets have gotten thinner. Plasma TV sets are so thin that you can hang them on a wall.