220-1101 Question 197
Single answerShielded twisted pairA technician is installing new Ethernet cabling for several desktop PCs in a small manufacturing office. The cable run must pass through an area with large electric motors and fluorescent lighting ballasts that have caused intermittent network errors on nearby unshielded copper runs in the past. The switch and patch panel both support standard RJ-45 Ethernet connections. Which cable type is the BEST choice to reduce electromagnetic interference in this environment while still using twisted-pair Ethernet?
- A
Shielded twisted pair (STP) cable
- B
Unshielded twisted pair (UTP) cable
- C
RG-6 coaxial cable
- D
Multimode fiber optic cable
Show answer and explanation
Correct answer: A
Explanation
The key issue in this scenario is electromagnetic interference from nearby industrial equipment. On the CompTIA A+ Core 1 exam, candidates should recognize that STP is used when copper Ethernet must operate in an electrically noisy environment. UTP is standard and less expensive, but it is not the best fit where EMI has already caused errors. Coax is shielded but not appropriate for standard modern Ethernet desktop connections through a switch and patch panel. Fiber is often the best medium overall for EMI-heavy areas because it is immune to electrical interference, but the question explicitly limits the solution to twisted-pair Ethernet. Best practice is to use shielded cabling where EMI is a concern and to ensure proper installation methods, including compatible connectors and grounding where required by the cable system design and manufacturer guidance.
- A. Correct.
Correct. Shielded twisted pair (STP) is specifically designed to reduce electromagnetic interference (EMI) and radio-frequency interference (RFI) by adding shielding around the pairs and/or overall cable bundle. In environments with electric motors, ballasts, or other electrically noisy equipment, STP is often the best twisted-pair choice. It still supports Ethernet over RJ-45-style connections when the installation is designed appropriately.
- B. Incorrect.
Incorrect. Unshielded twisted pair (UTP) is the most common Ethernet copper cabling and relies on the twisting of the pairs to reduce crosstalk and some external interference. However, in a known high-EMI environment such as one with large motors and fluorescent ballasts, UTP is more susceptible to interference-related errors than STP.
- C. Incorrect.
Incorrect. RG-6 coaxial cable is commonly used for cable television, broadband, and some video applications, not standard modern twisted-pair Ethernet desktop runs in an office LAN. A candidate might choose this because coax has shielding, but it is not the best answer for standard RJ-45 Ethernet switching in this scenario.
- D. Incorrect.
Incorrect. Multimode fiber optic cable is immune to EMI and would perform very well in electrically noisy environments. However, the question asks for the best choice while still using twisted-pair Ethernet. Fiber is not twisted-pair cabling, so it does not meet the stated requirement even though it may be an excellent alternative in other designs.