2.2 Data Transmission

Question 1

What is serial transmission?

Answer 1

Data is sent bit-by-bit along the same data line.

Question 2

What are 3 advantages of serial transmission?

Answer 2

Only requires 2 wires instead of 8 or 16 in parallel.
Serial can travel longer distances.
Serial has a more simple interface.

Question 3

What is a disadvantage of serial transmission?

Answer 3

It is much slower than parallel.

Question 4

What is parallel transmission?

Answer 4

All bits in a byte are sent simultaneously along separate lines.

Question 5

What is an advantage of parallel transmission?

Answer 5

It is much faster than serial transmission.

Question 6

What is a disadvantage of parallel transmission?

Answer 6

It cannot be used over as long a distance as serial (Due to interference along the cable)

Question 7

What is a Simplex data transmission process?

Answer 7

Where data transmission is possible in one direction only.

Question 8

What is a Half-Duplex data transmission process?

Answer 8

Where data transmission is possible in both directions but only in one direction at a time.

Question 9

What is a Full-Duplex data transmission process?

Answer 9

Where data transmission is possible in both directions simultaneously.

Question 10

What are 3 reasons for transmitting data digitally?

Answer 10

It is less likely to suffer corruption/degradation/interference.
It is possible to error check the data.
Can compress data therefore the transfer time is quicker.

Question 11

What is multiplexing?

Answer 11

It is where several independent data sources are combined to be sent along a single route to a single destination.

A multiplexor allows messages to be combined so they can be sent simultaneously and then separated again at the end of the link.

Question 12

What is Time Division Multiplexing?

Answer 12

Allocates small time slices alternately for data from each of the input message streams.

Question 13

What is Frequency Division Multiplexing?

Answer 13

Sends the messages simultaneously but uses different transmission frequencies.

Question 14

What is Switching?

Answer 14

Switching prevents all data being sent to all parts of a network and makes efficient use of the data lines.

Question 15

What is Circuit Switching?

Answer 15

A path is set up between sender and receiver and is released after transmission is complete.
Data is sent in order and cannot be used by any other traffic during that time.

Question 16

What is Packet Switching?

Answer 16

Data is split into packets which can take a different route through a network and may arrive out of order.
This means it is then re-assembled into the correct order.

Question 17

What does each packet carry during Packet Switching?

Answer 17

The actual data.
The order number of the packet.
Source and destination addresses.
Control signals.
Error control bits.

Question 18

Why is Packet Switching preferred?

Answer 18

It has better security as it can’t be intercepted.
It involves more efficient use of the data lines.
Less likely to be affected by a network failure.

Question 19

What is a switch?

Answer 19

It is used to connect computers in a local area network.

The switch is programmed with a table including IP address of all connected devices so data can be sent to the required device.

Packets of data are received and checked to determination the destination address.

Question 20

What is a router?

Answer 20

A router is used to forward data packets between networks and control traffic on wider area networks such as the internet.

It determines the destination of a data packet from the IP address and then selects an appropriate route for onwards transmission (Fastest Path).

Question 21

How can a data collision occur on a network?

Answer 21

When two sets of data are detected simultaneously on the network.
Each computer will then wait for a short time and send the data again.

Question 22

What is bandwidth?

Answer 22

It is a measure of how much data can be fitted onto a cable at any point in time.
Data still flows at the exact same speed.

Question 23

What is The Internet?

Answer 23

A world-wide communications infrastructure of interconnected packet-switched networks.
Consists of a number of specialist hardware components such as routers and switches.