CCTV Knowledge 3 — Questions and Answers
Question 1: What is the key difference between a DVR and an NVR in a CCTV system?
- A DVR records in color while an NVR records in black and white
- A DVR processes analog signals locally, while an NVR processes digital IP streams from network cameras (Correct answer)
- A DVR stores footage on tapes, while an NVR uses hard drives
- A DVR supports PTZ cameras, while an NVR does not
Correct answer: A DVR processes analog signals locally, while an NVR processes digital IP streams from network cameras
A DVR (Digital Video Recorder) encodes analog signals from traditional cameras, whereas an NVR (Network Video Recorder) records digital video streams from IP cameras over a network.
Question 2: Which lighting condition is IR (infrared) illumination designed to overcome?
- Excessive sunlight causing camera glare
- Complete or near-total darkness where visible light is insufficient (Correct answer)
- Flickering fluorescent lights causing frame-rate issues
- Fog and rain reducing image clarity
Correct answer: Complete or near-total darkness where visible light is insufficient
IR illuminators emit infrared light invisible to the human eye, allowing CCTV cameras with IR-sensitive sensors to capture images in total darkness.
Question 3: In CCTV system design, what does 'pixel density' determine?
- The power consumption of the camera sensor
- How much detail can be resolved in a given area of the image, affecting identification capability (Correct answer)
- The speed at which frames are captured per second
- The maximum cable length for the camera installation
Correct answer: How much detail can be resolved in a given area of the image, affecting identification capability
Pixel density (often measured in pixels per meter or PPM) determines image detail and is critical for achieving detection, recognition, or identification levels per surveillance standards.
Question 4: What is the purpose of PoE (Power over Ethernet) in IP camera installations?
- To increase the video resolution transmitted over Ethernet
- To deliver both data and electrical power to the camera over a single Ethernet cable (Correct answer)
- To encrypt the video stream for secure transmission
- To extend the cable distance beyond the standard 100-meter limit
Correct answer: To deliver both data and electrical power to the camera over a single Ethernet cable
PoE technology allows a single Cat5e/Cat6 cable to carry both the network data stream and the electrical power needed to operate an IP camera, simplifying installation.
Question 5: What is meant by 'frame rate' in CCTV video recording?
- The physical size of the camera housing in millimeters
- The number of individual images captured and displayed per second, measured in fps (Correct answer)
- The ratio of compressed file size to original file size
- The number of cameras supported by a single recording device
Correct answer: The number of individual images captured and displayed per second, measured in fps
Frame rate, measured in frames per second (fps), determines how smooth the recorded video appears; higher frame rates capture faster motion more accurately.
Question 6: Which compression standard offers the most efficient compression for IP cameras while maintaining high image quality?
- MJPEG
- H.264
- H.265 (HEVC) (Correct answer)
- MPEG-2
Correct answer: H.265 (HEVC)
H.265 (also called HEVC) provides approximately 50% better compression efficiency than H.264, significantly reducing storage and bandwidth requirements without sacrificing image quality.
Question 7: In the context of CCTV, what is a 'looping output' on a camera or monitor?
- A feature that automatically replays the last hour of recorded footage
- A secondary video output that passes the video signal through to another device without amplification loss (Correct answer)
- A setting that causes the camera to record continuously in a circular buffer
- A type of coaxial connector used for daisy-chaining cameras
Correct answer: A secondary video output that passes the video signal through to another device without amplification loss
A looping output allows a camera's video signal to pass through to another monitor or device in the chain, enabling the same signal to feed multiple destinations.
CCTV Knowledge 3
What is the key difference between a DVR and an NVR in a CCTV system?