DCI Testing and Certification 2 — Questions and Answers
Question 1: What does a wire map test verify in a copper cable installation?
- Signal attenuation at each frequency
- Correct pin-to-pin continuity and absence of miswires (Correct answer)
- The impedance of the cable pair
- Cable shielding effectiveness
Correct answer: Correct pin-to-pin continuity and absence of miswires
A wire map test confirms that each conductor is connected to the correct pin at both ends and identifies opens, shorts, reversals, and split pairs.
Question 2: Which parameter measures the ratio of signal power at a far-end receiver compared to the transmitted signal, indicating cable loss?
- NEXT
- Return Loss
- Insertion Loss (Correct answer)
- ELFEXT
Correct answer: Insertion Loss
Insertion Loss (formerly called attenuation) measures the reduction in signal strength as it travels along the cable from transmitter to receiver.
Question 3: A tester reports a 'split pair' fault. What condition does this describe?
- Two conductors from different pairs are wired together at both ends (Correct answer)
- One conductor is open at the far end
- The cable shield is not connected
- The pairs are reversed end-to-end
Correct answer: Two conductors from different pairs are wired together at both ends
A split pair occurs when conductors from two different pairs are substituted, creating correct continuity but causing excessive crosstalk due to unpaired conductors.
Question 4: What is the purpose of performing a Return Loss (RL) test on a copper link?
- To measure signal propagation delay
- To detect impedance mismatches that cause signal reflections (Correct answer)
- To verify the cable length is within specification
- To measure the DC resistance of each conductor
Correct answer: To detect impedance mismatches that cause signal reflections
Return Loss measures the amount of signal reflected back toward the source due to impedance discontinuities in the cabling.
Question 5: According to ANSI/TIA-568 standards, what is the maximum permanent link length for Category 6A horizontal cabling?
- 90 meters (Correct answer)
- 100 meters
- 70 meters
- 55 meters
Correct answer: 90 meters
The permanent link (from the telecommunications room to the work area outlet, excluding patch cords) is limited to 90 meters for all twisted-pair categories under TIA-568.
Question 6: What does PS-NEXT stand for in cable certification testing?
- Pair-Separated Near-End Crosstalk
- Power Sum Near-End Crosstalk (Correct answer)
- Phase-Shifted Noise Extinction Test
- Paired Signal Noise Evaluation Test
Correct answer: Power Sum Near-End Crosstalk
PS-NEXT (Power Sum Near-End Crosstalk) measures the combined crosstalk effect from all disturbing pairs simultaneously on a single victim pair.
Question 7: When testing fiber optic cable with an OTDR, what does a 'ghost' or 'echo' event indicate?
- A break in the fiber
- A reflective event appearing beyond the actual end of the fiber due to multiple reflections (Correct answer)
- A connector with high insertion loss
- A splice with excessive back-reflection
Correct answer: A reflective event appearing beyond the actual end of the fiber due to multiple reflections
A ghost event is a false reflection that appears beyond the fiber end caused by a high-reflectance event earlier in the trace bouncing multiple times.
DCI Testing and Certification 2
What does a wire map test verify in a copper cable installation?