hardMultiple ChoiceObjective-mapped
220-1201 Practice Question: A technician is deploying a new network in a…
A technician is deploying a new network in a warehouse and needs to measure the length of a spool of Cat6a cable before installation to ensure it does not exceed the 100-meter segment limit. Which tool should be used?
⚠ Common exam trap
Many candidates confuse a basic cable tester (which only checks continuity and wiring) with a TDR, assuming any 'cable tester' can measure length, but only a TDR (or a high-end certifier with TDR capability) can provide accurate length measurements.
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
✓
TDR (Time-Domain Reflectometer)
A Time-Domain Reflectometer (TDR) sends a pulse down the cable and measures the time it takes for the reflection to return from the far end or from a fault. By calculating the propagation velocity of the signal, the TDR can accurately determine the cable length, making it the correct tool to verify that a spool of Cat6a cable does not exceed the 100-meter segment limit before installation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Multimeter
Why it's wrong here
A multimeter is primarily designed to measure electrical properties such as voltage, current, and resistance. While it can detect basic continuity, its resistance measurement capabilities are not precise enough to accurately determine cable length, especially over the distances typically found in network deployments. It lacks the specialized functionality to account for the cable's velocity of propagation or to analyze signal reflections for distance calculation.
- ✗
Cable tester
Why it's wrong here
A standard cable tester is primarily used to verify basic connectivity, identify miswires, opens, shorts, and split pairs within a network cable. These basic testers confirm the integrity of the wiring scheme but do not possess the advanced capabilities required to measure the physical length of the cable. More sophisticated cable certifiers might integrate Time-Domain Reflectometer (TDR) functionality, but a generic 'cable tester' does not inherently provide length measurement.
- ✓
TDR (Time-Domain Reflectometer)
Why this is correct
A Time-Domain Reflectometer (TDR) is the ideal tool for measuring cable length by injecting a signal pulse into the cable and analyzing the reflections that return. By precisely measuring the time it takes for the reflected signal to return and knowing the cable's nominal velocity of propagation (NVP), the TDR accurately calculates the distance to any impedance discontinuity, including the cable's end. This makes it specifically suited for determining the exact length of installed cabling segments.
- ✗
Tone generator
Why it's wrong here
A tone generator, often used in conjunction with an inductive probe, is employed to trace and identify specific cables within a bundle or wall by injecting an audible tone onto the wire. This allows a technician to locate the corresponding cable at the other end, distinguishing it from many others. However, a tone generator provides no mechanism or functionality for measuring the physical length of the cable; its sole purpose is identification and tracing.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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