Английский язык: Методические указания и задания к контрольным работам для студентов специальности «Техническая эксплуатация транспортного оборудования», страница 17

2. Participle I, II – причастие настоящего времени, прошедшего времени.

     Для защиты контрольной работы студент должен владеть лексическим минимум, знать содержание текста и отвечать на вопросы по тексту, переводить предложения, знать образование грамматических моделей Passive Voice, Participle I, II.

Вариант 1

Задание №1 Прочитайте и переведите письменно текст:

Radio Transmitters

     Radio transmitters are designed to generate and radiate high frequency oscillations.

     The simplest transmitter consists of a radio frequency oscillator to produce high frequency signals, a transmitting antenna to radiate the signals, a battery or power source to supply electrical energy, and a key to interrupt the radiation of radio waves and thus convey intelligence.

     This type of transmission (radiotelegraphy) works well for broadcasting of code signals, but it cannot be used to transmit voice signals or music. When sounds of voice or music are converted into electrical signals by means of a microphone, these electrical waves vibrate at audio frequencies, between 16 cycles per second and 20.000 cycles per second (hertz).

     Signals cannot be efficiently radiated by themselves from an antenna to a receiver that is located at some distance from the transmitter. To transmit these audio signals it is necessary to impress them upon a radio wave (frequencies higher than 20,000 c.p.s.). This radio wave is then radiated from an antenna and thus carries the audio intelligence of signal with it. For this reason the radio wave is also known as a carrier wave (high frequency oscillations). Thus radio transmitters are designed to generate and radiate high frequency oscillations. The message to be transmitted (voice, music, telegraph signals, etc.) is superimposed onto these H.F. oscillations.

The block diagramme a radio transmitter includes the following main elements:

     MASTER OSCILLATOR (high frequency oscillator), whose function is to provide high frequency oscillations;

     POWER AMPLIFIER (radio frequency amplifier), designed to produce the required level of output power;

     ANTENNA for radiation of radio waves;

     MODULATOR by means of which the signal to be transmitted affects the high frequency oscillations. In the simplest case this can be a telegraph key, making and breaking the circuit.

     When the key is closed, the antenna radiates radio waves. When voice or music are transmitted the modulator causes the transmitter signal to vary according to the audio frequency variations.

VOCABULARY