VDV Video Distribution 4 — Questions and Answers
Question 1: What is the purpose of an EDID (Extended Display Identification Data) in an HDMI distribution system?
- Encrypt video content for copyright protection
- Communicate display capabilities to the video source (Correct answer)
- Regulate power supply to HDMI devices
- Convert frame rates between sources
Correct answer: Communicate display capabilities to the video source
EDID is a data structure that a display sends to the source device describing its supported resolutions, refresh rates, and audio formats so the source can output compatible signals.
Question 2: In a structured cabling environment, which TIA/EIA standard governs the installation of coaxial cable for video applications?
- TIA-568
- TIA-570 (Correct answer)
- TIA-606
- TIA-942
Correct answer: TIA-570
TIA-570 is the Residential Telecommunications Cabling Standard that covers coaxial and twisted-pair cabling for video, voice, and data in residential and light commercial buildings.
Question 3: What is the video bandwidth required for a standard definition NTSC composite video signal?
- 1 MHz
- 4.2 MHz (Correct answer)
- 13.5 MHz
- 27 MHz
Correct answer: 4.2 MHz
NTSC composite video has a maximum luminance bandwidth of 4.2 MHz, which defines the cabling and amplifier requirements for SD video distribution.
Question 4: A technician measures 0.3 Vp-p on a composite video signal that should be 1.0 Vp-p. What is the most likely cause?
- The signal frequency is too high
- Excessive cable attenuation or a missing DA (Correct answer)
- Incorrect frame rate
- Inverted sync polarity
Correct answer: Excessive cable attenuation or a missing DA
A drastically low signal level indicates cable loss has not been compensated, or a required distribution amplifier is absent from the signal path.
Question 5: Which video format carries both video and audio over a single cable using a BNC connector?
- Component video
- SDI (Serial Digital Interface) (Correct answer)
- S-Video
- VGA
Correct answer: SDI (Serial Digital Interface)
SDI carries uncompressed digital video with embedded audio channels multiplexed into the serial bitstream over a single 75-ohm coaxial cable with BNC connectors.
Question 6: What is the bit rate of HD-SDI used in 1080i/720p video distribution?
- 270 Mbps
- 1.485 Gbps (Correct answer)
- 3 Gbps
- 6 Gbps
Correct answer: 1.485 Gbps
HD-SDI operates at 1.485 Gbps (or 1.4835 Gbps for integer frame rates), supporting 720p60 and 1080i60 uncompressed video with embedded audio.
Question 7: When routing video signals through a building's conduit, what minimum bend radius should be maintained for RG-6 coaxial cable?
- 1 inch
- 3 inches
- 6 inches (Correct answer)
- 12 inches
Correct answer: 6 inches
RG-6 coaxial cable requires a minimum bend radius of approximately 6 inches (10× the cable diameter) to prevent deformation of the dielectric and impedance changes.
VDV Video Distribution 4
What is the purpose of an EDID (Extended Display Identification Data) in an HDMI distribution system?