Добавил:
Upload Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз: Предмет: Файл:
Ращинская 3 курс часть 2.doc
Скачиваний:
2
Добавлен:
09.11.2019
Размер:
857.09 Кб
Скачать

1 Learn the words & word combinations:

a manageable load

управляемая загрузка

multiple

множество

adjacent

соседний

appropriate

соответствующий

previous

предыдущий

remainder

остаток

permit

позволять

reference

ссылка

robust

надежный

relevant

соответствующий

reply

ответ

valid

действительный

advise

советовать

2 Find Russian equivalents; mind the meaning of these expressions:

  • for online signal processing

  • CCD single line image sensor

  • single line sensor assembly

  • multiple lens assembly

  • raster images

  • appropriate scanning time

  • an end of line code

  • redundant data

  • data compression encoder

  • group delay variation

  • data establishing machine parameters

  • sine and cosine modulated carriers

  • the symbol timing

  • redundancy means

3 Find English equivalents:

  • способный

  • термическая головка

  • теплочувствительная бумага

  • заботиться

  • независимый

  • близко

  • почти приведены в контакт с бумагой

  • отверстия

  • позволить

  • предыдущий

  • сдвиг

4 Answer the questions:

  1. How does a typical CCD scanner work?

  2. What is a second popular method of scanning?

  3. Explain the process of modulation & demodulation?

5 Translate in written form points

PART 3 (60.4.4 – 60.5)

60.4.4 Error correction mode

In CCITT ECM the transmitted signal is separated into HDLC frames so that on receive the FCS bytes allow the data accuracy to be checked. G3 transmission is half duplex and when the trans­mission stops the receiver replies giving the condition for each of the frames. The transmitter then selectively repeats the frames which the receiver advised were in error.

Figure 60.4 shows the ECM transmitted frame structure. Each frame contains 256 octets of image plus its frame number. A block can have up to 256 frames, equivalent to around 0.5Mbits of data, sufficient for most facsimile pages. In this case, if there are no errors, there are no additional turn rounds above a standard G3 transmissions.

If the pages are of greater data content than 0.5Mbit (about 50s at 9.6kbit/s) a partial page is generated at 256 frames. This partial page is corrected before proceeding with the next block. Following the image transmission a PPS is sent at 300bit/s to tell the receiver the page and block number and the actual number of frames in that block, for checking and recovery purposes.