VDV Video Distribution 5 — Questions and Answers
Question 1: In a CATV (cable television) distribution system, what device is used to combine multiple channel frequencies onto a single coaxial cable?
- Splitter
- Combiner/multiplexer (Correct answer)
- Directional coupler
- Tap
Correct answer: Combiner/multiplexer
A combiner (or RF multiplexer) passively merges multiple RF channel signals onto one coaxial cable for distribution without interference between channels.
Question 2: What is the function of a directional coupler in a CATV distribution system?
- Block reverse path signals
- Tap off a portion of signal with minimal main-line loss (Correct answer)
- Convert signal from coax to fiber
- Amplify signal in one direction only
Correct answer: Tap off a portion of signal with minimal main-line loss
A directional coupler taps a small percentage of the signal power for a branch while allowing the majority of the signal to continue down the main cable with minimal loss.
Question 3: Which fiber optic connector type is most commonly used in professional video distribution over fiber?
- RJ-45
- SC or LC (Correct answer)
- BNC
- F-type
Correct answer: SC or LC
SC and LC connectors are the standard single-mode and multimode fiber connectors used in professional video-over-fiber systems due to their low insertion loss and high precision alignment.
Question 4: A video over IP (VoIP video) system using MPEG-4 compression for distribution requires which network infrastructure consideration?
- Minimum 10BaseT switching
- Sufficient bandwidth and QoS prioritization (Correct answer)
- Analog phone line backup
- Serial RS-232 control bus
Correct answer: Sufficient bandwidth and QoS prioritization
Compressed video streams require guaranteed bandwidth and QoS (Quality of Service) settings to prevent packet loss, jitter, and latency that cause video artifacts.
Question 5: What is the purpose of a video equalizing amplifier in long-haul coaxial cable installations?
- Reduce the DC component of the signal
- Compensate for frequency-dependent cable losses (Correct answer)
- Convert from single-ended to balanced signal
- Remove sync pulses from the video signal
Correct answer: Compensate for frequency-dependent cable losses
Coaxial cable attenuates high frequencies more than low frequencies; an equalizing amplifier boosts higher frequencies proportionally to flatten the overall frequency response.
Question 6: In an AV-over-IP distribution system, what protocol is commonly used for multicast video streaming to multiple displays?
- FTP
- IGMP-managed multicast (Correct answer)
- SMTP
- SNMP
Correct answer: IGMP-managed multicast
IGMP (Internet Group Management Protocol) enables managed multicast, allowing a single video stream to be received by multiple endpoints without duplicating unicast traffic for each display.
Question 7: When a video technician notices picture rolling or loss of vertical sync on an analog monitor, what is the most likely cause?
- Excessive chroma saturation
- Corrupted or missing vertical sync pulses (Correct answer)
- Incorrect aspect ratio setting
- Audio-video lip sync offset
Correct answer: Corrupted or missing vertical sync pulses
Vertical sync pulses instruct the display when to begin each new frame; if they are missing or corrupt, the display cannot lock onto the frame timing and the picture rolls.
VDV Video Distribution 5
In a CATV (cable television) distribution system, what device is used to combine multiple channel frequencies onto a single coaxial cable?