11 Communication

Question 1

What is serial transmission?

Answer 1

The data packets are sent one after the other

Question 2

What is parallel transmission?

Answer 2

All data packets are sent at once along different wires

Question 3

List 4 advantages of serial transmission

Answer 3

1. Requires fewer wires therefore cheaper
2. Easy to set up as cable is flexible and thin
3. Not much interference
4. Doesn’t suffer from skew

Question 4

List 2 advantages of parallel transmission

Answer 4

1. Fast over short distances
2. Data doesn’t need to be ordered before sending

Question 5

Where is parallel transmission used?

Answer 5

Used in short range high speed applications e.g. data buses (used to be in printers)

Question 6

Where is serial data transmission used?

Answer 6

Used over long distances e.g. the internet

Question 7

What is synchronous transmission?

Answer 7

Data is transferred at regular intervals
The data is synchronized by a clock pulse
It allows large block of data to be sent continuously

Question 8

Where is synchronous transmission used and why?

Answer 8

Used in real time applications e.g. video chat
Because it is extremely fast

Question 9

What is asynchronous transmission?

Answer 9

One packet (8 bits) is sent at a time with a start and stop and parity bit
The computer starts reading at the start bit and stops at the stop bit

Question 10

What is asynchronous transmission used for

Answer 10

Lower speed transmissions e.g. WAN

Question 11

What are idling bits?

Answer 11

They are bits that fill in space until the next set of data arrives when no data is being sent in asynchronous transmission

Question 12

What is the difference between asynchronous and synchronous transmission

Answer 12

Asynchronous - data is sent in small packets at intervals
Synchronous - data is constantly being sent & changing this synchronized with a clock pulse

Question 13

What is bandwidth?

Answer 13

Bandwidth is a measure of how much information a channel is capable of carrying per second (bits per second)
(The maximum capacity)

Question 14

What is a channels baud rate?

Answer 14

The number of signal changes it is capable of per second

Question 15

What is baseband?

Answer 15

When a channel can only represent one bit per signal change

Question 16

How do you calculate bit rate?

Answer 16

Bit rate = Baud rate * bits per signal

Question 17

What is latency?

Answer 17

Latency is the delay between an action being started and the computer responding

Question 18

What is a protocol?

Answer 18

A strict set of rules for data transmission

Question 19

What is a handshake?

Answer 19

When two computers exchange signal in order to create a communication link

Question 20

How does handshaking work?

Answer 20

A - requests to transmit data
B - sends back acknowledgement
A - sends data to B
If no acknowledgement is received A will resend request

Question 21

What is a parity bit?

Answer 21

A bit added to the end of a binary string for error correction. It doesn’t contain any data but is used to ensure the string follows either even or odd parity. (Contains even or odd no of ones)
If the string doesn’t follow the desired parity it is resent as an error must have occurred.

Question 22

What is a check digit?

Answer 22

A digit added to the end of a code for error correction. (Used in barcodes)
An algorithm is performed on the main digits in the code and if the check digit and the result aren’t equal an error must have occurred so the data is resent.