Communications Systems practice questions

Correct: A — To the intersystem bonding termination

Per 800.100(B)(1), if the building has an intersystem bonding termination, the bonding conductor shall be connected to it — the other options are fallback points used only under 800.100(B)(2) or (B)(3) when no IBT exists.

Correct: C — No, 800.110(A)(2) excludes medium-power network-powered broadband cables from communications raceways

800.110(A)(2) states medium-power network-powered broadband communications cables shall not be installed in raceways complying with that section (communications raceways). Listing under 800.182 is a real requirement for communications raceways generally, but it doesn't override this specific exclusion. The cables aren't banned from all raceways — they're simply routed through Chapter 3 raceways instead, per 800.110(A)(1).

Correct: C — Power-limited fire alarm circuits under Article 760

800.133(A)(1) lists power-limited fire alarm systems (Article 760 Parts I and III) as permitted to share space with communications cables. Class 1 circuits are excluded under 800.133(A)(2), and electric light/power or non-power-limited fire alarm conductors require a barrier under 800.133(A)(3).

Correct: B — Only the sections of Chapters 1 through 7 specifically referenced within Chapter 8 apply

800.3 flips the usual pattern — Chapter 8 is largely self-contained, so a Chapter 1-7 rule applies only where Chapter 8 specifically calls it out. A blanket 'all apply' reading, a blanket 'none apply' reading, and a Class 2/3-only reading are all incorrect under 800.3.

Correct: D — 800.113(L)(1)

800.113(L)(1) covers uses permitted for communications wires, cables, cable routing assemblies, and communications raceways in one- and two-family dwellings outside the specific locations in (B) through (F). 800.113(G)(1) instead governs permitted uses for vertical riser runs specifically in one- and two-family dwellings, not general dwelling locations.

Correct: A — Drive a separate ground rod, bond the conductor to it, and connect the rod to the power grounding electrode system

800.100(A)(4) requires that when the overall length can't practicably be held to 6.0 m (20 ft) in a one- or two-family dwelling, a separate ground rod meeting the dimensional criteria of 800.100(B)(3)(2) or (B)(3)(3) be driven, with the bonding conductor connected to it and the rod then bonded to the power grounding electrode system. Upsizing the conductor or using a metal raceway doesn't address the length requirement — a raceway is a physical-protection measure under 800.100(A)(6), not a length workaround, and the 20 ft figure is a hard limit, not a suggestion.

Correct: C — A general-purpose communications cable

800.113(H)(1) permits plenum, riser, and general-purpose communications cables in cable trays. Limited-use cables, Type CMUC cables, and hybrid power-and-communications cables are all listed as not permitted under 800.113(H)(2).

Correct: A — 10 ft, because it can never exceed the 3 m absolute maximum

800.110(C)(1) allows a listing to extend support spacing beyond the 900 mm (3 ft) default, but 'in no case shall the distance between supports exceed 3 m (10 ft)' — that cap overrides even a listing that specifies more. So a 12 ft listed interval is not permitted; 10 ft is the hard ceiling.

Correct: D — A riser-rated communications cable

800.113(I)(1) permits plenum, riser, and general-purpose communications wires and cables at distributing frames and cross-connect arrays. Type BLU cable, limited-use cable, and hybrid power-and-communications cable are all specifically excluded by 800.113(I)(2).

Correct: B — The cable is plenum-rated and no more than 1.22 m (4 ft) long, associated with the air distribution system

800.113(B)(1) permits only plenum cable up to 1.22 m (4 ft) directly in the duct, provided it's associated with the air distribution system. Riser-rated cable of the same length is not the permitted category, and general-purpose cable is only allowed inside a 300.22(B) raceway, not a sleeve — a distinction from the actual rule text.

Correct: C — A bonding jumper not smaller than 6 AWG copper or equivalent between the two electrodes

Per 800.100(D), when a separate electrode is used for communications, a bonding jumper not smaller than 6 AWG copper or equivalent must connect it to the power grounding electrode system. Independently grounded electrodes are not permitted to stand alone — that's exactly the potential-difference hazard this rule prevents. The 4 AWG sizing tied to service conductors is not how this jumper is sized.

Correct: B — A grounding electrode installed in accordance with 800.100(B)(3)

Per 800.106(A)(1), when no mobile home service equipment is within 30 ft, the primary protector grounding terminal (along with the other listed components, if present) must connect to a grounding electrode per 800.100(B)(3). Tying to a water pipe or the neutral bus skips the specified electrode requirement, and grounding is never optional under this section.

Correct: A — A hybrid power and communications cable

Per 800.113(K)(2), hybrid power and communications cables are not permitted in multifamily dwellings outside the 800.113(B)-(G) locations. General-purpose cables, riser cables in riser raceways, and small-diameter limited-use cable in nonconcealed spaces are all listed as permitted under 800.113(K)(1).

Correct: B — 3 m (10 ft)

800.113(J)(1)(2) permits limited-use cables in these catch-all locations only up to a maximum of 3 m (10 ft) of exposed length in nonconcealed spaces. Longer runs, or claiming no limit, misstate the specific cap; 1.5 m understates it.

Correct: C — 800.44(B)

800.44(B) governs clearance of communications and CATV cables above roofs, including the reduced-clearance exceptions for limited overhang runs and sloped roofs. 800.44(A)(4) covers clearance for wires on poles, in-span, or between buildings/masts generally, not the roof-specific reductions; 800.44(C) and 800.44(D) address masts and between-building runs, not roof crossings.

Correct: C — 800.44(A)

800.44(A) sets the four conditions — relative location, cross-arm attachment, climbing space, and clearance — that govern communications wires sharing a pole or running parallel in-span with power conductors. 800.44(B) only addresses cables passing above a roof and 800.47(A) covers underground entries, so neither applies to this pole/span scenario.

Correct: C — It's not permitted; exposed general-purpose cable is specifically excluded under 800.113(C)(2)

800.113(C)(2) specifically excludes exposed general-purpose cable from plenum spaces. There's no 10-foot exposed-run exception, and general-purpose cable doesn't carry a plenum rating. The last option is too broad — plenum-rated cable is expressly permitted under 800.113(C)(1).

Correct: C — A general-purpose rated communications cable

800.113(G)(1) permits plenum, riser, and general-purpose cables in one- and two-family dwelling risers. Type BMU cable, hybrid power-and-communications cable, and bare communications wires are all listed as not permitted under 800.113(G)(2).

Correct: C — Riser communications raceway (innerduct) containing riser-rated cable

800.113(E)(1) permits riser communications raceway (innerduct) with riser-rated cable installed inside it. Cable routing assemblies, CMUC cable, and hybrid power-and-communications cables are all listed as not permitted under 800.113(E)(2).

Correct: B — 800.113(D)(1)

800.113(D)(1) is the Uses Permitted list specifically for cables, cable routing assemblies, and communications raceways installed in vertical riser runs penetrating floors or shafts. 800.113(C)(1) governs plenum spaces (environmental air handling), not vertical risers, and 800.113(F)(1) applies only when the riser is inside a fireproof shaft, a distinct condition from a general shaft/floor penetration.

Correct: B — 50 mm (2 in.)

800.133(B) sets the default separation at 50 mm (2 in.) between communications/CATV cables and electric light, power, Class 1, non-power-limited fire alarm, or medium-power network-powered broadband conductors. The larger distances are not the figure this section specifies, and 25 mm is too small to satisfy the rule.

Correct: A — No, because unlisted outside plant cable cannot be installed in an environmental air plenum regardless of length

800.48 permits unlisted outside plant cable only in building spaces other than risers, ducts for environmental air, plenums for environmental air, and other environmental air spaces — the plenum routing fails this condition regardless of the 15 m (50 ft) length being satisfied. The enclosure termination is correct for non-coax communications cable, but the space restriction is the violation here.

Correct: B — 610 mm (24 in.)

800.24(B) sets a specific 610 mm (24 in.) maximum support spacing for CI cable. The general 'neat and workmanlike' language in 800.24(A) applies to ordinary communications cable, but CI cable has its own stricter, distinct requirement rather than relying on general support practice.

Correct: B — Only if the cable is specifically listed and marked as part of a fire-resistive cable system

Per 800.179(E)(1), CI cable installed alone keeps its listed fire rating only in free air per 800.24. It's permitted in a raceway only where it's specifically listed and marked as part of a fire-resistive cable system, as covered in 800.179(E)(2). Raceway material and run length aren't the qualifying factors.

Correct: B — No — CM is listed for general-purpose use only, not risers or plenums

800.179(C) explicitly excludes risers and plenums from the general-purpose listing for CM cable — passing the flame-spread tray test doesn't expand where it can go. CMX is a limited-use type restricted to dwellings and raceway (800.179(D)), which is more restrictive, not less.

Correct: B — The maximum current per conductor the cable is listed to carry without exceeding its temperature rating

Per 800.179(F), the "-LP(XXA)" suffix designates the current limit in amperes per conductor, ensuring the cable's temperature rating isn't exceeded in bundles, raceways, cable trays, or cable routing assemblies. It is not a whole-bundle total, an overcurrent device size, or an inrush figure.

Correct: A — Listed as fire-resistant and low-smoke-producing, suitable for ducts and plenums

Per 800.179(A), cable in ducts, plenums, and other environmental air spaces (Type CMP, CATVP, BLP) must be listed as suitable for those spaces with fire-resistant and low-smoke-producing characteristics. Riser listing under 800.179(B) addresses vertical shafts, not air-handling spaces, and a CMR rating alone does not satisfy the plenum requirement.