Mississippi Communication Systems Examination

Under the Mississippi State Board of Contractors Communication Systems classification, energy-limited communication and low-voltage systems must not exceed which voltage?

• A24 volts
• B50 volts
• C91 volts
• D150 volts

Which of the following is specifically excluded from the Mississippi Communication Systems, Low Voltage Electrical classification?

• ATelephone systems
• BLow-voltage alarm systems
• CClosed-circuit video systems
• DSatellite dish antennas

Which installation is within the official MSBOC Communication Systems classification when it is energy limited and does not exceed 91 volts?

• AA 120-volt lighting branch circuit
• BA music-distribution and public-address system
• CA fire-detection control panel and initiating circuit
• DA service-entrance feeder to a panelboard

In the 2020 NEC, which article contains the general requirements that apply to communications systems unless modified by a later Chapter 8 article?

• AArticle 725
• BArticle 800
• CArticle 810
• DArticle 840

Which listed communications cable type is required in ducts, plenums, and other spaces used for environmental air?

• AType CM
• BType CMX
• CType CMP
• DType CMG

Communications cable installed in a vertical run that penetrates more than one floor, and that is not in a metal raceway or fireproof shaft, must be which type?

• AType CMX
• BType CM
• CType CMR or a higher listing such as CMP
• DType CATVX only

In a one- or two-family dwelling, which communications cable types are generally permitted for ordinary interior applications that are not plenum or riser spaces?

• AOnly Type CMP
• BType CM and Type CMX, as well as higher listings
• COnly unlisted outdoor station wire
• DOnly Type OFNP optical fiber

Which statement correctly describes the NEC communications-cable substitution hierarchy?

• AType CMX may be used in place of Type CMP
• BType CM may be used in place of Type CMR in an unprotected riser
• CType CMP may be used in place of Types CMR, CM, and CMX
• DType CMR may be used in place of Type CMP in a plenum

Per NEC 800.25, what must be done with the accessible portion of abandoned communications cable that is not identified for future use?

• ALeave it in place if it is not energized
• BPaint it red and coil it above the ceiling
• CRemove it
• DSplice it to the nearest active cable

Where a listed primary protector is required on a communications circuit, it shall be located:

• AAt the far end of the longest interior station run
• BAs close as practicable to the point of entrance
• COnly at the equipment rack, regardless of entrance location
• DOn the utility pole, never on the building

Under TIA-568 structured-cabling practice, the maximum permanent-link length of horizontal twisted-pair cable, not including work-area and patch cords, is:

• A55 meters (180 ft)
• B90 meters (295 ft)
• C100 meters (328 ft)
• D150 meters (492 ft)

What is the principal difference between T568A and T568B eight-position modular terminations?

• AT568A uses 75-ohm pairs and T568B uses 100-ohm pairs
• BThe orange pair and the green pair trade pin positions
• CT568B omits the brown pair
• DT568A is only for fiber and T568B is only for copper

In telephone and data cross-connects, a 110-block is generally preferred over a 66-block when the installer needs:

• AA termination rated for higher-frequency Category data cabling
• BA block that accepts only 25-pair 22 AWG station wire
• CA solder-only connection with no punch-down
• DA 75-ohm coaxial splitter

Why are balanced, shielded or twisted-pair microphone lines preferred over unbalanced TS lines on long sound-system runs?

• ABalanced lines cancel induced noise through common-mode rejection
• BBalanced lines always carry twice the speaker wattage
• CUnbalanced lines cannot pass audio below 1 kHz
• DBalanced lines eliminate the need for a mixer

On a standard 3-pin XLR microphone cable used for balanced audio, which assignment is correct?

• APin 1 signal hot, pin 2 shield, pin 3 unused
• BPin 1 shield/ground, pin 2 signal hot (+), pin 3 signal cold (−)
• CPin 1 signal cold, pin 2 shield, pin 3 phantom only
• DAll three pins are tied together as a speaker tap

Typical phantom power supplied by a mixer to a condenser microphone is:

• A12 V AC at the speaker terminals
• B48 V DC applied equally to the two signal conductors
• C70 V AC on the constant-voltage speaker line
• D120 V AC through the microphone cable shield

Which microphone type requires an external power source such as phantom power or an internal battery to operate?

• ADynamic moving-coil microphone
• BCondenser microphone
• CCarbon-button telephone transmitter only
• DPassive 70-volt ceiling speaker

What is the main installation advantage of a 70-volt (constant-voltage) distributed speaker system compared with a low-impedance 8-ohm system?

• AMany speakers can be wired in parallel and leveled by transformer taps without calculatin…
• BEach speaker must be series-wired until the total equals exactly 8 ohms
• CCable length no longer causes any high-frequency loss
• DThe system can legally include fire-alarm speakers under this MSBOC classification

A 120-watt 70-volt amplifier will feed ceiling speakers. Using the common 80-percent headroom practice, what is the maximum total of speaker-tap wattages that should be connected?

• A80 watts
• B96 watts
• C120 watts
• D150 watts

Two 8-ohm loudspeakers are connected in parallel to a low-impedance amplifier. What load does the amplifier see?

• A16 ohms
• B8 ohms
• C4 ohms
• D2 ohms

Standard coaxial cable used for CATV and most analog video distribution has which characteristic impedance?

• A50 ohms
• B75 ohms
• C100 ohms
• D8 ohms

Compared with RG-59, RG-6 coaxial cable is preferred for longer CATV or satellite runs primarily because it has:

• AA smaller center conductor and higher loss
• BA larger center conductor and lower attenuation at CATV frequencies
• CAn 8-ohm characteristic impedance
• DNo metallic shield, which reduces ground loops

The connector most commonly used on premises CATV and satellite coaxial drops is the:

• AF-type connector
• BXLR connector
• CspeakON connector
• DRJ11 connector

Analog closed-circuit video cameras commonly use which 75-ohm connector on the coaxial cable?

• ARJ45
• BBNC
• CNEMA 5-15
• DTS 1/4-inch phone

Which optical-fiber choice is generally used for long outdoor campus or utility-entrance backbone runs?

• AMultimode OM1 with LED sources only, regardless of distance
• BSingle-mode fiber with laser sources
• CCategory 3 unshielded twisted pair
• DRG-59 coaxial cable

47 CFR Part 68 governs which activity?

• AListing of plenum communications cable by UL
• BDirect connection of terminal equipment to the public switched telephone network
• CAmpacity of 12 AWG copper in NEC Table 310.16
• DOSHA fall-protection for aerial communications work

Under 47 CFR 68.213, a customer or premises owner may do which of the following?

• AInstall, remove, and rearrange wiring on the subscriber’s side of the demarcation point
• BOpen and service the carrier-installed primary protector
• CWork on carrier facilities on the network side of the demarcation point
• DMove the demarcation point onto the utility pole without carrier involvement

For a simple single-customer installation, 47 CFR 68.105 generally provides that the demarcation point shall not be located further inside the premises than:

• A12 inches from where the wiring enters the customer’s premises
• B10 feet from the service disconnect
• CThe first 110-block in the telecommunications room, regardless of entrance
• DThe far-end work-area outlet

Communications cable installed in the space above a suspended ceiling that is used as an environmental-air return must be:

• AType CM stapled to the ceiling grid
• BType CMP, or another method permitted for that air-handling space
• CType CMX because the run is short
• DAny outdoor-rated unlisted drop wire

NEC 805.133 generally prohibits placing communications circuit conductors in the same raceway, box, or enclosure with electric light, power, Class 1, or non-power-limited conductors unless:

• AThe communications cable is painted yellow
• BThe conductors are separated by a permanent barrier or another stated exception applies
• CThe power conductors are 12 AWG or smaller
• DThe run is less than 50 ft

TIA-568 horizontal cabling from the telecommunications room to each work-area outlet is installed in which topology?

• AA daisy-chained bus from outlet to outlet
• BA star from the horizontal cross-connect to each outlet
• CA ring that must return to the first outlet
• DA random free-topology splice network

Near-end crosstalk (NEXT) on twisted-pair data cable is reduced primarily by:

• AUntwisting each pair for 6 inches at every jack
• BMaintaining pair twists as close as practicable to the termination
• CRunning data cable in the same pipe as 480-volt feeders
• DUsing RG-59 instead of Category cable for 1000BASE-T

Insertion loss (attenuation) of a copper communications cable run increases when:

• AThe cable is shortened and the frequency is lowered
• BThe cable is lengthened or the signal frequency is raised
• CThe pairs are more tightly twisted
• DA higher Category listing is used at the same length and frequency

A commonly applied minimum bend-radius limit for 4-pair UTP during and after installation is about:

• AOne times the cable outside diameter
• BFour times the cable outside diameter
• CTwenty-five times the cable outside diameter
• DNo limit, because UTP has no bend-radius rule

When terminating Category 5e or Category 6 cable on a jack or 110-block, pair twists should be maintained:

• AOnly in the first 10 ft of the run
• BAs close as practicable to the insulation-displacement contacts
• CUntil the cable enters the room, then fully combed out
• DOnly on the orange pair

The correct basic signal-flow order in a live-sound reinforcement system is:

• ALoudspeakers → power amplifier → mixer → microphones
• BMicrophones → mixer/preamps → signal processing → power amplifier → loudspeakers
• CPower amplifier → microphones → loudspeakers → mixer
• DMixer → utility power panel → 70-volt taps → microphones

What is the primary purpose of a direct box (DI) between an instrument and a mixer?

• ATo convert a high-impedance unbalanced source to a low-impedance balanced microphone-leve…
• BTo step a 70-volt speaker line down to 8 ohms
• CTo supply 120 volts to a condenser microphone
• DTo combine two power-amplifier outputs in parallel

Acoustic feedback (howl-round) occurs when:

• AThe mixer is set for unity gain on unused channels
• BSound from the loudspeakers re-enters a live microphone with loop gain of 1 or more at so…
• CAll speaker taps are set to the lowest wattage
• DPhantom power is turned off on dynamic microphones

Compared with a 70-volt distributed system, a 25-volt constant-voltage system typically:

• ACarries more current for the same wattage and is used on shorter, smaller systems
• BAlways requires Type CMP cable
• COperates the speakers at 480 volts
• DCannot use transformer taps

Outdoor receiving antennas and satellite dish installations are covered in which 2020 NEC article?

• AArticle 210
• BArticle 640
• CArticle 810
• DArticle 830

An IP closed-circuit camera typically uses which premises cabling media and connector?

• ARG-59 coaxial cable with a BNC connector only
• BFour-pair balanced twisted pair with an 8-position modular (RJ45) connector
• CTwo-conductor 18 AWG speaker wire with wire nuts
• DRG-6 with an F-connector only, regardless of camera type

In structured cabling, backbone (riser) cabling is the cabling that:

• ARuns from a work-area computer to a monitor
• BInterconnects telecommunications rooms, equipment rooms, and entrance facilities
• CMust always be RG-59
• DReplaces the need for a horizontal cross-connect

A 60 Hz hum that appears when an audio system and the building electrical system share multiple ground paths is commonly called a:

• AGround loop
• BSpeaker tap
• CNEXT failure
• DPlenum listing

Using P = V² / R and 70.7² ≈ 5,000, what impedance does a 70-volt speaker present when it is tapped at 10 watts?

• A8 ohms
• B70 ohms
• C500 ohms
• D5,000 ohms

Which CATV coaxial listing is required in a plenum (environmental-air) space?

• ACATVX
• BCATV
• CCATVR
• DCATVP