- A
Tone generator
Why wrong: A tone generator is used for cable tracing, not for measuring interference.
- B
Cable certifier
A cable certifier can measure noise levels and signal quality, helping identify EMI from external sources like fluorescent lights.
- C
Ping
Why wrong: Ping can show packet loss but cannot pinpoint the cause as EMI versus other issues.
- D
Wi-Fi analyzer
Why wrong: A Wi-Fi analyzer is for wireless networks, not for detecting interference on UTP cables.
Question 213 of 1,020
How to Use a Cable Certifier to Confirm Electromagnetic Interference
This 220-1201 practice question tests your understanding of networking tools. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 small office has intermittent network dropouts. A technician suspects electromagnetic interference (EMI) from nearby fluorescent lights affecting the unshielded twisted-pair (UTP) cables. Which tool can best confirm the presence of EMI on the cable?
Quick Answer
The answer is a cable certifier, as this is the only tool that can quantitatively confirm electromagnetic interference (EMI) on a cable. Unlike a simple continuity tester or tone generator, a cable certifier measures signal-to-noise ratio (SNR) and detects excessive noise levels, providing the hard data needed to prove that nearby fluorescent lights are corrupting the signal on unshielded twisted-pair (UTP) cabling. On the CompTIA A+ Core 1 220-1201 exam, this question tests your ability to distinguish between basic verification tools and advanced diagnostic equipment; a common trap is choosing a tone probe or multimeter, which cannot measure interference. Remember that a certifier “certifies” the cable’s performance against standards, while a simple tester only checks for physical continuity. For a quick memory tip, think “Cable Certifier = EMI Confirmer,” since only this tool can give you the SNR numbers to back up your suspicion.
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
✓
Cable certifier
A cable certifier is the correct tool because it can measure crosstalk, return loss, and other electrical characteristics that reveal the presence of EMI on UTP cables. Unlike simple continuity testers, a certifier performs frequency-domain analysis (e.g., up to 500 MHz for Cat6a) to detect noise and interference that cause intermittent dropouts.
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.
- ✗
Tone generator
Why it's wrong here
A tone generator is used for cable tracing, not for measuring interference.
- ✓
Cable certifier
Why this is correct
A cable certifier can measure noise levels and signal quality, helping identify EMI from external sources like fluorescent lights.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Ping
Why it's wrong here
Ping can show packet loss but cannot pinpoint the cause as EMI versus other issues.
- ✗
Wi-Fi analyzer
Why it's wrong here
A Wi-Fi analyzer is for wireless networks, not for detecting interference on UTP cables.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The CompTIA A+ exam often tests the distinction between tools that verify physical-layer compliance (certifier) versus tools that only indicate symptoms (ping) or operate on different media (Wi-Fi analyzer), leading candidates to mistakenly choose ping because it shows packet loss during dropouts.
Trap categories for this question
Command / output trap
Ping can show packet loss but cannot pinpoint the cause as EMI versus other issues.
Detailed technical explanation
How to think about this question
A cable certifier applies a swept-frequency signal and measures the cable's return loss, NEXT (Near-End Crosstalk), and ACR (Attenuation-to-Crosstalk Ratio) to quantify noise margins. In real-world scenarios, EMI from fluorescent ballasts often induces common-mode noise that a certifier detects as increased impedance anomalies or reduced signal-to-noise ratio, even when the cable appears physically intact.
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.
What to study next
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Networking Tools — This question tests Networking Tools — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Cable certifier — A cable certifier is the correct tool because it can measure crosstalk, return loss, and other electrical characteristics that reveal the presence of EMI on UTP cables. Unlike simple continuity testers, a certifier performs frequency-domain analysis (e.g., up to 500 MHz for Cat6a) to detect noise and interference that cause intermittent dropouts.
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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