Вопрос № 884775 - Английский язык

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Radio Systems
1. Radio systems used for communications will have the following elements. With more than 100 years of development, each process is implemented by a wide range of methods, specialized for different communications purposes. Each system contains a transmitter. This consists of a source of electrical energy, producing alternating current of a desired frequency of oscillation. The transmitter contains a system to modulate some property of the energy produced to impress a signal on it.
2. This modulation might be as simple as turning the energy on and off, or altering more subtle properties such as amplitude, frequency, phase, or combinations of these properties. The transmitter sends the modulated electrical energy to a tuned resonant antenna; this structure converts the rapidly changing alternating current into an electromagnetic wave that can move through free space.
3. The electromagnetic wave is intercepted by a tuned receiving antenna; this structure captures some of the energy of the wave and returns it to the form of oscillating electrical currents. At the receiver, these currents are demodulated, which is conversion to a usable signal form by a detector sub-system. The receiver is «tuned» to respond preferentially to the desired signals, and reject undesired signals.
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Варианты ответов
  • All radio systems consist of the same elements and therefore are designated for the same communication purposes.
  • Radio systems have a long history of application because they are of great use due to the simplicity of their working.
  • A radio system is implemented by a wide range of methods, specialized for different communications purposes.
  • In spite of being designated for various communications purposes such radio systems contain the same elements working on the same principles.
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Вопрос задал(а): Анонимный пользователь, 13 Ноябрь 2020 в 15:35
На вопрос ответил(а): Анастасия Степанова, 13 Ноябрь 2020 в 15:35