2.1 Data Tranmission

Question 1

What is ‘bit rate’?

Answer 1

Rate at which data is transferred

Question 2

What is ‘serial transmission’?

Answer 2

• Uses a single wire
• Low cost
• Used over longer distances
• Slow (low bit rate), only one bit at a time
• Safer transmission (easier to reassemble at the other end)

Question 3

What is ‘parallel transmission’?

Answer 3

• Uses multiple wires
• Used over shorter distances
• More expensive
• Quicker tranmission
• Less safe, more opportunity for errors to occur

Question 4

What is ‘interference’?

Answer 4

Disturbances that can occur in the wires/signals during the data transfer that may corrupt or delay it

Question 5

What is ‘simplex transmission’?

Answer 5

• Data is only ever sent in one direction

- TV & radio

Question 6

What is ‘full duplex transmission’?

Answer 6

• Data is sent in two directions simultaneously

- Phone call

Question 7

What is ‘half duplex’ transmission?

Answer 7

• Data can be sent it either direction
• BUT only one direction at a time
• Walkie-Talkie

Question 8

What is ‘Checksum’?

Answer 8

• When both the devices sending and receiving data check with each other if they have counted the same number of bits
• If they ARE the same, the all the data has been transmitted
• If they ARE NOT the same then they know some data was lost or corrupted and can ask for it to be sent again

Question 9

What is a ‘Parity check’?

Answer 9

-The last digit of each 8-bit number that is sent states whether it is an odd number or even number. If a number is odd, another odd number is added to make it even.

Question 10

What are ‘Check digits’?

Answer 10

• An error detection method
• Used with bar codes and bank account numbers
• Commonly used to check for/correct human error

Question 11

What is an ‘Automatic Repeat Request’?

Answer 11

• The rules for error control
• It looks for errors in packets of data that it receives
• It automatically asks the sender to resend only the packets which it detected errors in