DCI Copper Installation 5 — Questions and Answers
Question 1: What is the minimum separation distance between copper data cables and electrical conduit carrying circuits of 2–5 kVA in open runs?
- 1 inch
- 2 inches
- 5 inches (Correct answer)
- 12 inches
Correct answer: 5 inches
ANSI/TIA-569 requires a minimum 5-inch (127 mm) separation between data cables and electrical conduit carrying 2–5 kVA to prevent EMI.
Question 2: What test verifies that each pair in a copper cable has approximately the same propagation delay?
- Propagation delay skew (Correct answer)
- Insertion loss
- Return loss
- ELFEXT
Correct answer: Propagation delay skew
Propagation delay skew measures the difference in signal travel time between the fastest and slowest pairs, which must be within 45 ns for Cat6/6A.
Question 3: A technician is pulling Category 6A cable in a conduit. The conduit fill is already at 40%. What should the technician do?
- Pull the cable anyway since 40% fill is acceptable
- Install a larger conduit or a parallel conduit run (Correct answer)
- Remove existing cables and re-bundle them tighter
- Use Cat6 instead, which has a smaller diameter
Correct answer: Install a larger conduit or a parallel conduit run
NEC and TIA-569 limit conduit fill to allow cable pulling without damage; at 40% fill adding more cable would exceed limits and risk damaging all cables.
Question 4: When testing a newly installed copper link, a 'FAIL – Return Loss' result most likely indicates what problem?
- A cable that is too long
- Impedance discontinuities caused by kinks, tight bends, or bad terminations (Correct answer)
- Incorrect T568A/B wiring standard selection
- A missing pair in the cable
Correct answer: Impedance discontinuities caused by kinks, tight bends, or bad terminations
Return loss failures are caused by impedance discontinuities in the cable path, such as kinks, excessively tight bends, over-tightened cable ties, or poor terminations.
Question 5: What is the function of a gel-filled splice case in copper outside plant (OSP) installations?
- To amplify signal strength over long runs
- To protect copper splice joints from moisture ingress (Correct answer)
- To convert copper to fiber at a cross-connect point
- To ground the cable shield to the building steel
Correct answer: To protect copper splice joints from moisture ingress
Gel-filled splice cases enclose and seal copper cable splices in outdoor environments, preventing water intrusion that would degrade performance or cause shorts.
Question 6: Which measurement parameter is used to evaluate the performance of a cable from end to end, combining both NEXT and attenuation?
- Return loss
- ACR-N (Attenuation to Crosstalk Ratio, Near-End) (Correct answer)
- Propagation delay skew
- DC loop resistance
Correct answer: ACR-N (Attenuation to Crosstalk Ratio, Near-End)
ACR-N (formerly called ACR) is calculated as NEXT minus insertion loss and represents the signal-to-noise ratio at the near end of the link.
Question 7: What is the correct method to handle excess cable slack at a work area outlet?
- Coil it tightly behind the outlet box
- Store it in a service loop with a diameter no less than 8 times the cable OD (Correct answer)
- Cut it flush with the back of the outlet box
- Fold it in half and staple it to the stud
Correct answer: Store it in a service loop with a diameter no less than 8 times the cable OD
Excess cable should be stored as a service loop with a minimum diameter of 8 times the cable's outer diameter to avoid exceeding the minimum bend radius.
DCI Copper Installation 5
What is the minimum separation distance between copper data cables and electrical conduit carrying circuits of 2–5 kVA in open runs?