Вопрос № 933115 - Английский язык

Amplitude and signal phase changes due to a radio transmitter or a radio receiver travelling through radio communication system and/or signal propagation through inhomogeneous medium is …

Прочитайте текст и выполните задания.
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.
Ответьте на вопрос:
Why does a modulation system serve for in a transmitter?

Прочитайте текст и определите, какой из заголовков соответствует тексту.
Signals can be either analogue or digital. In an analogue signal, the signal is varied continuously with respect to the information. In a digital signal, the information is encoded as a set of discrete values (for example ones and zeros). During transmission the information contained in analogue signals will be degraded by noise. Conversely, unless the noise exceeds a certain threshold, the information contained in digital signals will remain intact. This noise resistance represents a key advantage of digital signals over analogue signals.

Прочитайте текст и определите, какой из заголовков соответствует тексту.
A collection of transmitters, receivers or transceivers that communicate with each other is known as a network. Digital networks may consist of one or more routers that route information to the correct user. An analogue network may consist of one or more switches that establish a connection between two or more users. For both types of network, repeaters may be necessary to amplify or recreate the signal when it is being transmitted over long distances. This is to combat attenuation that can render the signal indistinguishable from noise.

Прочитайте текст и определите, какой из заголовков соответствует тексту.
A channel is a division in a transmission medium so that it can be used to send multiple streams of information. For example, a radio station may broadcast at 96.1 MHz while another radio station may broadcast at 94.5 MHz. In this case, the medium has been divided by frequency and each channel has received a separate frequency to broadcast on. Alternatively, one could allocate each channel a recurring segment of time over which to broadcast – this is known as time-division multiplexing and is sometimes used in digital communication.

Прочитайте текст и заполните пропуски подходящими по смыслу словами.
Mobile phones have had a significant impact on 1_______ networks. Mobile phone subscriptions now outnumber fixed-line subscriptions in many markets. Sales of mobile 2_______ in 2005 totalled 816.6 million with that figure being almost equally shared amongst the markets of Asia/Pacific (204 m), Western Europe (164 m), CEMEA (Central Europe, the Middle East and Africa) (153.5 m), North America (148 m) and Latin America (102 m). Increasingly these phones 3_______ by systems where the voice content is transmitted digitally such as GSM or W-CDMA choosing to depreciate analogue 4_______ such as AMPS.