- A
The cable is not properly terminated with RJ45 connectors.
Why wrong: Improper termination usually causes complete failure, not intermittent interference.
- B
The cable is not shielded (STP).
UTP cable lacks shielding, making it vulnerable to EMI from nearby electrical equipment.
- C
The cable length exceeds the maximum for Cat6.
Why wrong: Cat6 supports up to 100 meters, so 50 meters is well within limits.
- D
The cable is a crossover cable.
Why wrong: Crossover cables are used for direct device connections, not related to interference.
Question 658 of 1,020
UTP Cable and EMI Interference from Fluorescent Lights
This 220-1201 practice question tests your understanding of cabling. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A user complains that their VoIP phone intermittently loses connectivity. The phone is connected to a switch via a 50-meter run of solid-core Cat6 cable. You suspect interference from nearby fluorescent lights. Which cabling characteristic is most relevant to this issue?
Quick Answer
The answer is that the cable is not shielded (STP). Unshielded twisted pair (UTP) cable lacks the metallic foil or braided shielding that protects against electromagnetic interference (EMI), making it vulnerable to noise sources like fluorescent lights. When a long 50-meter run of UTP Cat6 passes near such lights, the EMI can corrupt the digital signal, causing intermittent VoIP connectivity drops. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of how environmental factors degrade network performance—a common trap is assuming Cat6’s higher frequency rating makes it immune to EMI, when in fact shielding is the key differentiator. Remember the mnemonic: “UTP Unprotected, STP Saved.”
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The cable is not shielded (STP).
Fluorescent lights generate electromagnetic interference (EMI), which can disrupt data transmission over unshielded twisted-pair (UTP) cabling. Shielded twisted-pair (STP) cable includes a conductive shield that protects against EMI, making it the relevant characteristic for this issue. The user's intermittent connectivity is likely caused by EMI coupling onto the UTP cable, and using STP would mitigate this.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The cable is not properly terminated with RJ45 connectors.
Why it's wrong here
Improper termination usually causes complete failure, not intermittent interference.
- ✓
The cable is not shielded (STP).
Why this is correct
UTP cable lacks shielding, making it vulnerable to EMI from nearby electrical equipment.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The cable length exceeds the maximum for Cat6.
Why it's wrong here
Cat6 supports up to 100 meters, so 50 meters is well within limits.
- ✗
The cable is a crossover cable.
Why it's wrong here
Crossover cables are used for direct device connections, not related to interference.
Common exam traps
Common exam trap: answer the scenario, not the keyword
In the CompTIA A+ exam, this question tests understanding of how electromagnetic interference (EMI) from sources like fluorescent lights affects UTP cabling and the importance of using shielded twisted-pair (STP). The trap is that candidates may incorrectly attribute the issue to cable length or termination, overlooking that interference is a shielding problem, not a distance or connector issue.
Detailed technical explanation
How to think about this question
EMI from fluorescent lights typically couples onto UTP cables via common-mode noise, which can corrupt differential signals if the cable's twist ratio is insufficient to reject the interference. STP cables use a foil or braided shield that must be properly grounded at both ends to be effective; improper grounding can create ground loops, worsening the issue. In real-world deployments, running UTP parallel to fluorescent ballasts for more than a few meters often requires STP or fiber to maintain signal integrity.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Cabling — This question tests Cabling — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The cable is not shielded (STP). — Fluorescent lights generate electromagnetic interference (EMI), which can disrupt data transmission over unshielded twisted-pair (UTP) cabling. Shielded twisted-pair (STP) cable includes a conductive shield that protects against EMI, making it the relevant characteristic for this issue. The user's intermittent connectivity is likely caused by EMI coupling onto the UTP cable, and using STP would mitigate this.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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