О. В. Фёдорова е. В. Мезина е. В. Хамис английский язык в сфере информационных технологий и коммуникаций учебное пособие

Wireless telecommunications use radio waves, sent through space from one antenna to another, as the medium for communication. Radio waves are used for receiving AM and FM radio and for receiving television. Cordless telephones and wireless radiotelephone services, such as cellular radiotelephones and pagers, also use radio waves. Telephone companies use microwaves to send signals over long distances. Microwaves use higher frequencies than the radio waves used for AM, FM, or cellular telephone transmissions, and they can transmit larger amounts of data more efficiently. Microwaves have characteristics similar to those of visible light waves and transmit pencil-thin beams that can be received using dish-shaped antennas. Such narrow beams can be focused to a particular destination and provide reliable transmissions over short distances on Earth. Even higher and narrower beams provide the high-capacity links to and from satellites. The high frequencies easily penetrate the ionosphere (a layer of Earth’s atmosphere that blocks low-frequency waves) and provide a high-quality signal.