Mitigating EMI with Shielded Twisted Pair Cabling

N10-009 By islever Editorial Last updated

Given a scenario, use appropriate IP v4 network addressing. Given a scenario, troubleshoot common cabling and physical interface issues.

Short answer

D Shielded twisted pair should be used to mitigate high levels of electromagnetic interference from kitchen appliances while maintaining lower costs compared to fiber optics.

Question

After a recent building renovation, the number of tickets regarding network slowness during lunch breaks increases. A cable from the server room is traced to the break room, which has high levels of known interference. Which of the following types of network cables should be used to address this issue while keeping costs low?
  1. Single-mode fiber
  2. Multimode fiber
  3. Unshielded twisted pair
  4. Shielded twisted pair Correct Answer

Key Takeaways

The core trap is choosing fiber for immunity without considering the 'keep costs low' constraint, or choosing UTP while ignoring the severity of the interference.

This N10-009 question addresses network cabling selection in high-interference environments. Shielded twisted pair (STP) is the correct solution to block EMI from appliances while keeping costs low.

Common mistake: Candidates often select Unshielded twisted pair (C) because it is the standard default for most office installations. They fail to account for the specific 'high levels of known interference' mentioned in the scenario, leading to continued connectivity issues.

Expert Analysis

The scenario presents a classic electromagnetic interference (EMI) problem. The break room experiences network slowness specifically during lunch breaks, which correlates with the heavy use of microwave ovens and other kitchen appliances that generate significant EMI. The prompt explicitly states the cable is in an environment with "high levels of known interference." To mitigate EMI, the cabling must provide protection against external electrical noise.

Unshielded twisted pair (UTP), while common and low-cost, relies solely on wire twisting to cancel out interference; it offers no defense against high-level EMI sources like microwaves. Therefore, UTP is unsuitable here. Fiber optic cables (both single-mode and multimode) are immune to EMI because they transmit light rather than electricity. However, fiber is significantly more expensive than copper solutions due to higher material costs and the need for specialized transceivers and termination equipment. The question emphasizes keeping costs low, making fiber an impractical choice despite its technical superiority regarding immunity.

Shielded twisted pair (STP) provides a metallic foil or braid shield around the twisted pairs, effectively blocking external EMI. STP maintains the lower cost profile of copper cabling while offering the necessary protection against the specific interference described. Thus, STP is the optimal balance of performance and cost for this constraint.

Official Reference

https://aom.com/networking/what-is-the-difference-between-stp-and-utp/

This link opens the official vendor documentation in a new tab.

Exam Strategy

Always scan for environmental constraints first. When a question mentions 'interference,' 'motors,' or 'microwaves,' immediately rule out unshielded media. If the question also specifies a budget constraint or 'low cost,' avoid fiber optics even though they are immune; choose shielded copper instead.

Frequently Asked Questions

Why not use fiber optic cable since it is immune to EMI?

Fiber is immune to EMI but is significantly more expensive than copper cabling. The question explicitly requires keeping costs low, making STP the more appropriate economic choice.

Does twisting wires in UTP protect against microwave interference?

Twisting helps cancel out some crosstalk and mild interference, but it is insufficient against high-intensity EMI sources like microwave ovens operating nearby.

More N10-009 FAQ →

Discussion 3 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 3

  1. AnderSpain 👍 1 Answered D
    For Question 683, the correct answer is D. Shielded twisted pair (STP). 🔍 Why is this the correct answer? The interference problem: The statement mentions that a cable was run from the server room to the break room, a location with high levels of known interference (e.g., appliances such as microwaves or other electrical equipment). The shielding solution: Shielded twisted-pair (STP) cables have a protective metallic layer surrounding the internal wire pairs. This effectively mitigates electromagnetic interference (EMI) and crosstalk caused by noisy environments, unlike unshielded twisted-pair (UTP) cables, while maintaining a relatively low cost compared to using only fiber optic cable.
  2. ERB14 👍 1 Answered D
    The correct answer is D. Shielded twisted pair. High Interference Cause: The break room likely contains appliances like microwave ovens, which operate heavily during lunch breaks and cause significant electromagnetic interference (EMI).
  3. Skri113xX 👍 1 Answered B
    My initial thought is B, and after re-reading, I'm sticking with it.

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