Television and telecommunication

Television is a widely used telecommunication medium for sending (broad-

casting) and receiving moving images, either monochromatic (black and white) or color, usually accompanied by sound.

In its early stages of development, television included only those devices employing a combination of optical, mechanical and electronic technologies to capture, transmit and display a visual image. As it is known, all modern television systems are based on electronic technologies, however the knowledge gained from the work on mechanical-dependent systems was important in the development of electronic television.

In 1884 Paul G. Nipkow, a 20-year old university student in Germany invented the first electromechanical television system which employed a scanning disk, a spinning disk with a series of holes spiraling toward the center, for “rasterization”, the process of converting a visual image into a stream of electrical pulses. The beginning of the 20-th century brought advances in amplifier tube technology and the use of a rotating mirror-drum scanner to capture the image. Most of the 20-th century television sets depended also upon the cathode-ray tube invented by Karl Braun in 1921.

Telecommunication, transmission of signals over a distance for the purpose of communication, is an important part of modern society. In telecommunication, a communication system is a collection of individual communications networks, transmission systems, relay stations, substations and data terminal equipment usually capable of interconnection and interoperation to form an integral whole. The components of a communication system serve a common purpose, they are technically compatible, use common procedures, respond to controls and operate in unison.

Radar

The word “radar” means Ra dio D etermination a nd R anging. Radar equipment is capable of determining by radio echoes the presence of objects, their direction, range and recognizing their character. Radar detects objects at a distance by reflecting radio waves off them. The delay caused by the echo measures he distance. The direction of the beam determines the direction of the reflection. The polarization and frequency of the return can sense the type of surface.

There are several types of radar sets, all of them consisting of six essential components, namely: a transmitter, a receiver, an antenna system, an indicator, a timer and, of course, a power supply.

A radar set detects by sending out short powerful pulses of ultra-high frequency radio wave energy from a high power transmitter. The directional antenna takes this energy from the transmitter and radiates it in a beam (similar to that of a searchlight). As the transmitted energy strikes an object, a portion of it is reflected back. The receiver picks up the returning echo through its antenna and translates it into visual readable signals on a fluorescent screen. The appearance of these signals show the presence of an object within the field of view of radar.

Navigational radars scan a wide area two to four times per minute. They use very short waves that reflect from earth and stone. They are common on ships and long-distance aircraft. General-purpose radars generally use navigational radar frequencies, but modulate and polarize the pulse so he receiver can determine the type of surface of the reflector. Search radars scan a wide area with pulses of short radio waves and sometimes use the Doppler effect to separate moving vehicles from clutter. Weather radars can even measure wind speed.

4. Coordinate the words given in the left column with their interpretation in

the right: