VDV Cabling Infrastructure 4

Question 1

What is the maximum length of a work area cable (equipment cord) between a wall outlet and an end device in TIA-568?

Accepted Answer

10 meters

Answer

TIA-568 allows up to 10 meters total for combined equipment cords at both ends of a horizontal channel, though individual work area cords are typically kept to 5 meters or less.

Question 2

When testing installed fiber with an OTDR, a 'ghost' reflection appears beyond the far end of the fiber. What is the most likely cause?

Accepted Answer

A high-reflectance event re-reflecting back past the launch end

Answer

Ghost reflections occur when a very strong Fresnel reflection (e.g., an open, polished end) bounces back to another high-reflectance point and re-reflects, appearing as a false event beyond the actual fiber end.

Question 3

Which backbone cabling topology is recommended by TIA-568 for campus environments?

Accepted Answer

Hierarchical star

Answer

TIA-568 recommends a hierarchical star topology for backbone cabling, with the campus distributor connecting to building distributors, which connect to floor distributors.

Question 4

A technician measures a near-end crosstalk (NEXT) loss of 28 dB on a Cat5e link. What does this result indicate?

Accepted Answer

The link fails because Cat5e requires a minimum of 35 dB NEXT at 100 MHz

Answer

Cat5e requires a minimum NEXT loss of 35.3 dB at 100 MHz per TIA-568-C.2; a reading of 28 dB indicates insufficient isolation between pairs, meaning the link fails certification.

Question 5

What grounding method is used to protect coaxial cable shields in a video distribution system from lightning and power induction?

Accepted Answer

Bonding the shield to the building ground at each cable entry point

Answer

NEC Article 820 requires that coaxial cable shields be bonded to the building's ground electrode system at the point where cables enter the structure to divert surge currents safely.

(VDV) Voice Data Video Technician Certified Practice Test

(VDV) Voice Data Video Technician Certified Practice Test

VDV Cabling Infrastructure 4