Digital transmission

Analog transmission has been in use for many years as the basis of telephone technology and is very effective for this purpose, but it is not so suitable for high-speed transmission of information. Digital transmission consists of electrical pulses representing data in binary code as a series of 5 on/off pulses. A number of different codes exist, some of which are based on a 6-, 7-, or 8-bit structure. ASCII is a 7-bit code and EBCDIC is an 8-bit code. The codes represent characters, transmission control signals, information separators, and device control. Digital technology has a number of advantages compared to analog, including higher transmission 10 speed, lower incidence of errors, and the facility for mixing data consisting of voice, image, and text on the same circuit. It is for this reason that data transmissions will be increasingly digital in the future. A network structure known as Integrated Services Digital Network (ISDN) facilitates these aspects.

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I I I

I

C L

Task 12

Speaking

Work in pairs, A and B. Use the information in this unit to describe the diagrams below. You may make notes first.

Student A: Describe diagram 1 to your partner.

Cc

Local computer

M

M

Remote computer

Student B: Describe diagram 2 to your partner.

M

AC

L

AC - Acoustic coupler CC -Clustercontroller M - Modem MP - Multiplexor PC - Personal computer T - Terminal

c

t

"t

Task 13

Writing

Write a paragraph to show the difference between analog and digital transmission.

i

Task 14

Across

1 ~^ A combination of electronic devices and conductors that form a conducting

path. (7)

2 i An agreement that covers the procedures used to exchange information

between co-operating computers. (8)

3 j This kind of transmission has been the basis for telephone technology for many

years, though it is gradually being replaced. (6)

4 To send programs or data from a central computer to a remote PC. (8)

5 Single vib ations of electric current. (7)

6 ^A A VDU screen and keyboard used to interact with a computer, usually with no

computing capacity of its own. (8)

7 This kind of transmission consists of electrical signals representing data in
binary code. (7)

8 A public database, for example, that can be accessed over a computer or
telephone network. (6,7)

9 A____ controller controls a number of similar peripheral device such as

terminals and links them to the main computer. (7)

10 This merges information from several channels into one channel. (11)

11 A device that converts the computer's digital bit stream into an analog signal
for transmission over a telephone line. (5)

12 A____ board is a public teleconferencing system that allows users to read and

write messages. (8)

Down

13 The process of sending signals electronically. (12)

Language focus C

Word formation: suffixes

We have already seen how prefixes can change the meaning of a word. Let us now consider some suffixes, their usual meanings, and how they change the meanings of English words.

Suffixes

2 Verb-forming suffixes:

Suffix

Meaning

Examples

-ize/-ise -ate

-ify -en

to make

computerize automate, activate, calculate simplify harden, widen

3 Adverb-forming suffix:

Suffix

Meaning

Examples

-ly

in the manner of

electronically, logically, comparably, helpfully

4 Adjective-forming suffixes:

Suffix

Meaning

Examples

-al -ar -ic -ical

-able -ible

-ous

-ful

-less

-ish

-ed -ive

having the quality of

capable of being

Tike, full of

characterized by

without

like

having the quality of

computational, logical

circular

magnetic, automatic

electrical

comparable divisible

dangerous

helpful

careless

yellowish

computed interactive

Exercise 2

Note: Words ending in -ing are formed from verbs. The -ing form may be used as a noun, part of a noun phrase, or part of a verb.

Examples:

1 Programming is an interesting job. (noun)

2 Programming in C is interesting, (part of noun phrase)

3 He is working as a programmer, (part of verb)

Read the following sentences and circle the suffixes. Underline the stem if it can be used on its own. The first one has been done for you.

A program nxg) designs, writes, and tests programs for perfomx ln^ various tasks on a comput@).

A systems analyst studies organizational systems and decides what action needs to be taken to maximize efficiency.

3 Laser printers are preferable to other types of printing devices because of their
speed and quietness.

4 The microcomputer we have purchased does not have a FORTRAN compiler. It
is programmable in BASIC only.

5 We have found that operators who have the freedom to take short breaks
during the day greatly improve their performance.

6 The number of shipments will increase over the coming months.

7 We decided to computerize the entire plant to give each division more
independence.

8 Spooling is a way of storing data temporarily on disk or tape until it can be
processed by another part of the system.

9 Turning your office into a paperless environment may be expensive at the
beginning but can produce big savings in the long run.

10 Software developers are producing increasingly sophisticated applications for a growing global market.

Now, for each word that has a suffix, indicate what part of speech the word is (e.g. noun, verb, etc.).

Taski

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