Interference as the cause of transmission errors

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Which best describes interference in data transmission?

A A method that checks data after it arrives

B Unwanted disturbance to a signal that can damage data while it travels

2. Which is an example of interference?

A Electrical noise from a motor near a cable

B A parity bit added to a byte

3. What is crosstalk?

A Signal from one cable leaking into a nearby cable

B Two computers confirming they received data

4. Interference can cause a bit to change from 0 to 1 during transmission.

A False

B True

5. Which link is usually MORE exposed to interference?

A A long wireless link

B A short cable between two nearby devices

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1interference		AInterference has changed one bit during transmission, so the data has been changed
2Sent: 10110010 Received: 10100010		BThe comparison is the wrong way round. Longer and wireless links are more exposed to interference, so the wireless 100m link has the higher risk.
3Crosstalk is when the signal in one cable leaks into a cable next to it and disturbs the data there		CUnwanted disturbance to a signal, such as electrical noise, that damages data while it travels
4Longer or wireless links are more exposed to interference, so errors are more likely		DcableA signal -> leaks into cableB
5interference = data sent twice		EInterference is not data being sent twice. It is unwanted disturbance, such as electrical noise or crosstalk, that damages the signal and the data it carries.
6risk(wired 1m) > risk(wireless 100m)		Flink_length up => error_risk up

Definitions

interference

Fill in the Blanks

Complete each line of code by filling in the missing parts.

sent ← "10110010" received ← "10010010" IF sent _ received THEN

interference ← TRUE IF ____________ THEN OUTPUT "Bits may change"

signal ← "weak" IF signal = "weak" THEN ______ "Data may be damaged"

IF cableLength > 90 THEN risk ← "high" _____

IF link = "wireless" __ length > 90 THEN risk ← "high" ENDIF

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A sent = "10110010"

B received = "10100010"

C if sent == received:

D print("Data changed")

Question 2

A sent = 1

B noise = 1

C received = sent + noise

D print(received)

Question 3

A distance = 100

B limit = 50

C if distance < limit:

D print("More exposed")

Question 4

A neighbour_signal = True

B if not neighbour_signal:

C print("Crosstalk risk")

Question 5

A wire = "unshielded

B if wire == "unshielded":

C print("Picks up noise")

Answer Key

Interference as the cause of transmission errors

Section A: Quick Questions

B — Unwanted disturbance to a signal that can damage data while it travels

A — Electrical noise from a motor near a cable

A — Signal from one cable leaking into a nearby cable

B — True

A — A long wireless link

Section B: Match the Pairs

interference → Unwanted disturbance to a signal, such as electrical noise, that damages data while it travels

Sent: 10110010 Received: 10100010 → Interference has changed one bit during transmission, so the data has been changed

Crosstalk is when the signal in one cable leaks into a cable next to it and disturbs the data there → cableA signal -> leaks into cableB

Longer or wireless links are more exposed to interference, so errors are more likely → link_length up => error_risk up

interference = data sent twice → Interference is not data being sent twice. It is unwanted disturbance, such as electrical noise or crosstalk, that damages the signal and the data it carries.

risk(wired 1m) > risk(wireless 100m) → The comparison is the wrong way round. Longer and wireless links are more exposed to interference, so the wireless 100m link has the higher risk.

Section C: Definitions

interference — Unwanted disturbance to a signal, such as electrical noise or crosstalk, that damages data as it travels and can cause bits to be lost, gained or changed.

Section D: Fill in the Blanks

sent ← "10110010"
received ← "10010010"
IF sent ≠ received THEN

interference ← TRUE
IF interference THEN
  OUTPUT "Bits may change"

signal ← "weak"
IF signal = "weak" THEN
  OUTPUT "Data may be damaged"

IF cableLength > 90 THEN
  risk ← "high"
ENDIF

IF link = "wireless" OR length > 90 THEN
  risk ← "high"
ENDIF

Section E: Spot the Error

C — The warning should appear when the data sent and received are different, because interference has changed a bit. The test should be sent != received.

C — Noise flips a bit, so the result must still be 0 or 1. The XOR operator ^ flips the bit when noise is 1. Adding gives 2, which is not a valid bit.

C — Longer links are more exposed to interference. The message should print when the distance is greater than the limit, so the test should use >.

B — Crosstalk happens when signals leak from a neighbouring cable. The risk exists when a neighbour signal is present, so the test should be if neighbour_signal: without not.

A — The string is missing its closing quote, which is a syntax error. It should be wire = "unshielded".