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220-1201 Practice Question: A company's IT department is deploying new VoIP…
A company's IT department is deploying new VoIP phones. After connecting a phone to a PoE switch, the phone does not power on. The switch port is configured for PoE and shows no errors. Which tool should be used to verify that the Ethernet cable delivers power correctly?
⚠ Common exam trap
Candidates often choose 'Cable tester' (Option A) because they assume a cable tester can verify PoE delivery, but a standard cable tester only checks continuity and pinout, not voltage or power presence.
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
✓
Multimeter
A multimeter is the correct tool because it can measure DC voltage directly on the Ethernet cable's power-carrying pairs (typically pins 4,5 and 7,8 for Mode A or pins 1,2 and 3,6 for Mode B in 802.3af/at PoE). By probing the switch-side pins while the phone is connected, you can verify whether the switch is actually delivering the expected 48V DC, isolating a cable or power issue. This is the only tool among the options that can confirm the presence of voltage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Cable tester
Why it's wrong here
A basic cable tester primarily verifies the continuity and correct wiring (pinout) of individual conductors within an Ethernet cable, ensuring there are no open circuits, shorts, or crossed pairs. While essential for basic cable integrity, it lacks the sophisticated circuitry to detect the presence or measure the specific DC voltage levels required for Power over Ethernet (PoE) delivery, which is crucial for powering VoIP phones.
- ✗
Tone generator
Why it's wrong here
A tone generator, often used in conjunction with a probe, injects an audible signal onto a specific cable pair, allowing technicians to physically locate and identify a particular cable within a bundle or wall. Its sole function is cable tracing and identification, not electrical measurement. It provides no capability to assess voltage, current, or the operational status of PoE delivery to a device.
- ✓
Multimeter
Why this is correct
A digital multimeter (DMM) is a versatile diagnostic tool capable of measuring various electrical properties, including DC voltage. When set to measure DC voltage, it can be used to directly test the power-carrying pairs (typically pins 1,2,3,6 or 4,5,7,8, depending on the PoE standard) of an Ethernet cable. This allows an IT technician to accurately verify if the required 48V DC (or other standard PoE voltage) is present and being delivered to the VoIP phone.
- ✗
Wi-Fi analyzer
Why it's wrong here
A Wi-Fi analyzer is a specialized software or hardware tool designed to detect, analyze, and troubleshoot wireless network signals (802.11 standards). It provides information about signal strength, channel utilization, interference, and access point configurations. Since VoIP phones in this scenario are being deployed using wired Ethernet connections and require Power over Ethernet (PoE), a Wi-Fi analyzer is completely irrelevant for diagnosing power delivery issues on a physical cable.
Go deeper
Related to this question
Learn chapter
Power Supply Units and Connectors
Key term
Ethernet
Ethernet is a wired networking technology that connects devices like computers, printers, and servers to each other and to the internet using cables.
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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