Module 6 Chapter 1 Communication Methods Flashcards Preview

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Flashcards in Module 6 Chapter 1 Communication Methods Deck (38)
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1

What is meant by data communication?

Sending and receiving data from one computer or device to another.

2

Give three common applications of data communication.

- Sending and receiving e-mails
- Making and receiving calls on mobile phones
- Requesting and fetching data from a server

3

Is data communication limited to data transferred across separate computer systems?

No, data communication takes place with all computer systems, between the CPU and its peripheral devices such as a disk drive.

4

What are the two alternative methods of data transmission we use?

- Serial data transmission
- Parallel data transmission

5

What is serial data transmission?

When data is sent from source to destination over a single cable, one bit at a time.

6

What is parallel data transmission?

When several bits are sent simultaneously over a number of parallel wires to transmit data from source to destination.

7

What are the advantages of serial data transmission over parallel data transmission?

- Very high bit rates can be achieved (depending on the type of cable, fibre-optic cables being very fast)
- Data can be easily transmitted over longer distances
- No problem with skew or crosstalk as found in parallel data transmission
- Serial cables are cheaper in general
- Serial connectors typically take up less space

8

What is the typical range of data transfer rates achieved by serial data transmission?

50 Megabits per second (Mbs) to 100 Gigabits per second (Gbs)

9

Where is parallel data transmission normally used?

Within a computer system. Parallel cables are often used for computer buses. Parallel cables can also be used to transmit data over short distances ,a couple of metres at most, connecting devices such as a PC and a nearby printer.

10

What is the advantage of using parallel data transmission?

More bits can be transferred at once, which can lead to a faster transfer rate, but not always as the baud rate can be severely limited.

11

What two problems with parallel data transmission can cause corrupted data at higher signal frequencies?

- Crosstalk: interference between parallel lines
- Skew: bits travelling parallel lines at different rates

12

What is crosstalk?

A problem that occurs in parallel data transmission where parallel lines interfere with each other, corrupting the data. This is worsened by higher signal frequencies and transmitting data over longer distances.

13

What is skew?

When variations in the exact properties of individual wires in a parallel connection cause bits to travel across them at different speeds and arrive at their destination out of order, causing data to be corrupted. For this reason, parallel data transmission is only reliable over short distances and signal frequencies are limited.

14

When would you use serial data transmission?

When you need to transfer data across distances over about two metres.

15

What is protocol?

A set of rules relating to communication between devices.
In order to allow equipment from different suppliers to be networked, a standardised set of rules (protocols) has to be implemented, covering standards for physical connectors, cabling, mode of transmission, speed, data format, error detection and correction methods. Any pieces of equipment which use the same communication protocol can be networked.

16

What is bit rate?

The speed at which data is transmitted, measured in bits per second.

17

What is baud rate?

The rate at which the signal changes, so how quickly the signal can go from 1 to 0 or 0111 to 0100. It is measured in 'units' per second.

18

How do you calculate bit rate?

bit rate = baud rate * number of bits per signal

19

What is baseband?

Baseband is when bit rate is equal to baud rate. In other words, the number of bits per signal is one.

20

What is bandwidth?

The amount of data that can be transmitted in a fixed amount of time. It is usually expressed in bits per second (bps). Bandwidth is essentially the maximum bit rate of a signal.

21

What is latency?

Latency is the time delay between the moment the first byte of a communication leaves the source and when it arrives at its destination.

22

What is a parity bit?

The last bit in a byte, used for error checking.

23

What are the two types of parity?

- Odd parity, where the number of 1's must be odd
- Even parity, where the number of 1's must be even

24

Assuming no error has occurred, does the following byte use even or odd parity?
00010110

Odd parity.

25

Assuming no error has occurred, does the following byte use even or odd parity?
01010110

Even parity.

26

A computer system is using an even parity system and needs to transmit the following seven digit binary number:
0011101
What would the parity bit be?

0

27

A computer system is using an even parity system and needs to transmit the following seven digit binary number:
1011101
What would the parity bit be?

1

28

A computer system is using an odd parity system and needs to transmit the following seven digit binary number:
0011101
What would the parity bit be?

1

29

A computer system is using an odd parity system and needs to transmit the following seven digit binary number:
1011101
What would the parity bit be?

0

30

A computer system is using an odd parity system and transmits the following byte:
01101001
Has an error occurred?

Yes; there's an even number of 1's.

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