CHAPTER 14 TELEVISION

Television is the offspring of three media - the

theater, film and radio. In a relatively short period (about

45 years), television has progressed from a mere

novelty, to arguably, the most powerful information and entertainment medium. The technological advancements of television in

this short time frame are quite remarkable. Color television sets virtually replaced black-and-white models, cable television eliminated the need for viewers to tune in broadcast channels with "rabbit ear" antennas, and videotape, videotape machines and character generators (CGs) signaled the end of 16mm television film and cumbersome production equipment and methods.

The military services recognized the potential of this new form of communication and started Armed Forces Television at Limestone Air Force Base, Maine, in 1953. The success of this experimental station convinced DoD officials that overseas television stations were feasible. One year later, the DoD officially recognized the television mission and combined it with Armed Forces Radio to form the Armed Forces Radio and Television Service (AFRTS). In 1976, the CNO established the Navy Broadcasting Service (NBS) to manage AFRTS outlets within the DON. Most likely, your initial television broadcasting experience will be with an NBS detachment overseas or aboard a ship equipped with a Shipboard Information, Training and Entertainment (SITE) system. For these reasons, you are responsible for knowing the basics of this fascinating but demanding medium.

HOW TELEVISION WORKS

LEARNING OBJECTIVE: Identify how the television medium works.

Television is the process of converting reflected light rays from a subject or scene into electrical impulses and reproducing these impulses at a distant receiver.

The television camera picks up reflections of light from the scene, while the microphone picks up sound. The camera changes the light reflections into electrical impulses, and at the same time, the microphone changes the sound into electrical impulses. These impulses are sent to the transmitter or are recorded on videotape.

To be viewed, the signal from the transmitter is received by the viewer's television set, or the recording is played back - either to the transmitter or directly to a receiver. At the receiver, the picture and sound signals are isolated and sent through separate picture and sound circuits. Electronic components within your television set change these signals back to video on the cathode-ray picture tube and audio on the television speaker.

THE TELEVISION CAMERA

LEARNING OBJECTIVE: Recognize the basic operation, electronic characteristics and main types of television cameras.

The television camera is the heart of the television system. It records the varying amounts of light reflected from objects in the televised scene. This amount of light varies according to the lighting, color or shade of the object. Figure 14-1 shows a banner with the word NAVY printed in black on a white background. The border

Figure 14-1. - The various amounts of light seen by the television camera.

Figure 14-2. - The scanning process.

around the banner is gray. When light hits the banner, it reflects from the three different shades in different amounts. The white background reflects the most light, the gray reflects less, and the word NAVY reflects very little light. From this you can see that a scene made up of different shades or colors reflects different amounts of light. The television camera takes these various levels of light reflection and changes them into electrical impulses of varying strength.

A television camera is optically similar to a movie camera, except it does not use film. Instead, light reflections from the scene are focused by a lens and pass through the face of the photoelectric transducer (also called a pickup tube) of the camera. The pickup tube does the job of film in a camera. Its surface is coated with thousands of tiny globules of silver mixed with other chemical elements. This coating is photosensitive, which means it gives off electrons when exposed to light. Light from the scene covers the entire surface of the pickup tube and electrons are forced off its rear surface. The number of electrons forced off any part of the pickup tube is determined by the amount of light that strikes this part.

In figure 14-1, the Navy banner causes the pickup tube to give off electrons corresponding to the amount of light reflected from various parts of the banner.

At the present time, there is no practical method for transmitting a complete video picture instantaneously as a whole unit. Therefore, in television, the picture is broken into tiny units called elements, which are transmitted individually in sequence. The elements are so small that the human eye cannot distinguish one from

the other in the complete picture. The process of registering all the elements of a video picture in sequence is called scanning. During the scanning process, the television camera "encodes" the elements; then the television receiver is used to "decode" them in the proper order to recreate the original image (fig. 14-2).