CCTV CCTV Power and Cabling Infrastructure 2 — Questions and Answers
Question 1: What is the maximum cable length for a standard Cat6 Ethernet run used for IP CCTV cameras?
- 50 meters
- 100 meters (Correct answer)
- 250 meters
- 500 meters
Correct answer: 100 meters
The IEEE 802.3 standard specifies a maximum segment length of 100 meters for Cat5e/Cat6 Ethernet cable used in IP networks including IP cameras.
Question 2: What device is used to extend IP camera cable runs beyond the 100-meter Ethernet limit?
- Video balun
- Ethernet switch or media converter (Correct answer)
- Video amplifier
- Coax splitter
Correct answer: Ethernet switch or media converter
An Ethernet switch regenerates the signal at each hop, or a fiber media converter can extend the run over much longer distances using fiber optic cable.
Question 3: What is a 'video balun' used for in CCTV installations?
- Converting between PAL and NTSC video formats
- Transmitting video over UTP (twisted pair) cable instead of coax (Correct answer)
- Amplifying weak video signals over long distances
- Converting analog video to IP format
Correct answer: Transmitting video over UTP (twisted pair) cable instead of coax
A video balun converts the unbalanced coaxial cable signal to a balanced signal suitable for transmission over UTP twisted-pair cable.
Question 4: Which grounding issue commonly causes 'hum bars' (horizontal rolling lines) in analog CCTV footage?
- Overloaded PoE switch ports
- Ground loop interference between equipment at different potentials (Correct answer)
- Incorrect frame rate settings on the DVR
- Excessive cable length without amplification
Correct answer: Ground loop interference between equipment at different potentials
Ground loops occur when two pieces of equipment are grounded at different electrical potentials, inducing 50/60Hz AC interference into the video signal.
Question 5: What does 'conduit fill ratio' refer to in CCTV cable installation planning?
- The percentage of a conduit's cross-sectional area occupied by cables (Correct answer)
- The ratio of shielded to unshielded cables in a run
- The number of splices per conduit length
- The proportion of power to data cables in shared routing
Correct answer: The percentage of a conduit's cross-sectional area occupied by cables
Conduit fill ratio is the percentage of the conduit's interior cross-section occupied by cables; NEC guidelines typically limit fills to 40% for multiple cables to ensure heat dissipation and cable pull ease.
Question 6: What is the advantage of using fiber optic cable for long-distance CCTV camera runs?
- It is cheaper than coaxial cable
- It is immune to electromagnetic interference and supports very long runs (Correct answer)
- It natively supports PoE power delivery
- It requires no transceivers at either end
Correct answer: It is immune to electromagnetic interference and supports very long runs
Fiber optic cable transmits data as light pulses, making it immune to EMI and RFI, and supports runs of several kilometers without signal degradation.
CCTV CCTV Power and Cabling Infrastructure 2
What is the maximum cable length for a standard Cat6 Ethernet run used for IP CCTV cameras?