VDV Network Infrastructure 5 — Questions and Answers
Question 1: What is the maximum allowable pair untwist at a termination point per TIA-568 for Cat6 cable?
- 6 mm (0.25 inch)
- 13 mm (0.5 inch) (Correct answer)
- 25 mm (1 inch)
- 50 mm (2 inches)
Correct answer: 13 mm (0.5 inch)
TIA-568-C.2 limits pair untwist at terminations to 13 mm (0.5 inch) for Cat6 to maintain crosstalk performance at the connection point.
Question 2: Which test parameter measures the signal leakage from one pair to an adjacent pair at the same end of the cable being tested?
- NEXT (Near-End Crosstalk) (Correct answer)
- FEXT (Far-End Crosstalk)
- Return Loss
- Insertion Loss
Correct answer: NEXT (Near-End Crosstalk)
NEXT measures the unwanted signal coupling from a transmitting pair to an adjacent pair measured at the same end of the cable, which is the most critical crosstalk parameter.
Question 3: In a structured cabling design, what is the maximum recommended horizontal cable run length including the patch cords?
- 90 meters channel / 100 meters total
- 100 meters channel with up to 10 meters for patch cords
- 90 meters for the permanent link, with total channel up to 100 meters (Correct answer)
- 55 meters for Cat6, 100 meters for Cat6A
Correct answer: 90 meters for the permanent link, with total channel up to 100 meters
TIA-568 specifies a 90-meter permanent link for horizontal cabling, with up to 10 meters allocated for patch cords and equipment cords for a 100-meter total channel.
Question 4: What is the primary advantage of using shielded twisted pair (STP) cable versus unshielded twisted pair (UTP) in a VDV installation?
- STP supports longer runs without signal repeaters
- STP provides improved immunity to electromagnetic interference (EMI) (Correct answer)
- STP is less expensive to install
- STP does not require grounding at terminations
Correct answer: STP provides improved immunity to electromagnetic interference (EMI)
The metallic shield in STP cable reduces susceptibility to external EMI sources, making it preferred in environments with heavy electrical equipment or interference.
Question 5: A network closet has a switch with a faulty uplink to the MDF. The technician needs to verify the fiber patch cable is good. Which test should be performed first?
- OTDR trace from the MDF
- Visual inspection and optical power meter test (Correct answer)
- Full cable certification with a certifier
- Replace the fiber with copper and test
Correct answer: Visual inspection and optical power meter test
Visual inspection for physical damage followed by an optical power meter test is the fastest and most practical first step to verify patch cable integrity.
Question 6: What does the term 'headend' refer to in a CATV or video distribution system?
- The customer's TV set or display device
- The central facility where signals are received, processed, and distributed (Correct answer)
- The amplifier closest to the end user
- The coaxial splitter at the building entrance
Correct answer: The central facility where signals are received, processed, and distributed
The headend is the central processing facility that receives satellite, off-air, or other signals, processes them, and distributes the combined signal to subscribers.
Question 7: Which IEEE standard defines the specifications for Wi-Fi 6 (802.11ax) wireless networking?
- IEEE 802.11ac
- IEEE 802.11n
- IEEE 802.11ax (Correct answer)
- IEEE 802.11ad
Correct answer: IEEE 802.11ax
IEEE 802.11ax is the standard that defines Wi-Fi 6, featuring OFDMA, MU-MIMO improvements, and BSS Coloring for improved performance in dense environments.
VDV Network Infrastructure 5
What is the maximum allowable pair untwist at a termination point per TIA-568 for Cat6 cable?