To determine your level of knowledge of digital video recorders, take our Twenty Questions quiz. Then turn to page 30 to find out how you scored.
1. How many frames per second are generally
perceived as real-time video?
a. 1
b. 15
c. 30
d. All of the above
2. A mathematical method of creating missing image pixels is called
a. interpolation.
b. artifacts.
c. Active X.
d. None of the above
3. NTSC is the most prevalent video standard in North America.
a. True
b. False
4. PAL is the most prevalent video standard in Europe.
a. True
b. False
5. WINIPCFG is the command used to check an IP address in Windows XP.
a. True
b. False
6. Multiple DVRs connected to a common LAN can share a single IP address.
a. True
b. False
7. Which factor determines the maximum storage capacity of a DVR?
a. Image size
b. Frames per
second stored
c. Size of hard drive
d. All of the above
e. None of the above
8. Which of the following is an example of a CODEC?
a. JPEG
b. MPEG
c. Wavelet
d. All of the above
e. None of the above
9. Which of the following communication protocols divides messages into packets?
a. TCP
b. UDP
c. IP
d. All of the above
e. None of the above
10. Which of the following communication protocols can provide the fastest speed?
a. TCP
b. UDP
c. IP
d. All of the above
e. None of the above
11. DVRs can allow remote viewing of live and recorded images over a a. LAN.
b. POTS line.
c. the Internet.
d. Any of the above
e. None of the above
12. What information is necessary in order to connect a DVR to a network for remote offsite viewing?
a. IP address
b. Gateway
c. Subnet mask
d. All of the above
e. None of the above
13. DVRs can control recording based upon a. motion.
b. time of day.
c. alarm input.
d. Any of the above
e. None of the above
14. The data capacity of a network is referred to as its
a. bandwidth.
b. bridge.
c. cache.
d. None of the above
15. An IP address consists of 3 octets separated by periods.
a. True
b. False
16. Video images stored by a DVR can be
a. sent via email.
b. saved to remov-
able media.
c. printed to a
standard printer.
d. Any of the above
e. None of the
above
17. Which of the following is an advantage of using DVRs over analog VCRs?
a. Higher image quality
b. Ease of searching
c. Lower
maintenance
d. All of the above
e. None of the above
18. What type of jack is needed to connect a DVR to a LAN?
a. RJ-11
b. RJ-31X
c. RJ-45
d. Any of the above
e. None of the above
19. Multiplexers cannot be used with DVRs.
a. True
b. False
20. Image data saved to a CD has a unlimited shelf life.
a. True
False
What Went Wrong with VCR Replacement?
The security industry’s bane installer, Wally ‘Larman, was asked to replace an old analog VCR with a DVR. The existing system included two 9-position multiplexers, each with their own CCTV monitor and an analog VCR connected to one of the multiplexers. In addition to adding the DVR, the customer wanted to maintain the existing CCTV monitors and multiplexers so that he and his partner could control which images were displayed at their desks. When Wally began working he discovered that the nearest multiplexer did not have any available looping outputs so he T-tapped the coaxial cables at the nearest multiplexer and ran RG-59U cables to the DVR location, as shown in this diagram. When Wally was finished the customer was not happy with the quality of the images. Can you see what Wally did wrong and what he should do to correct the problem?
What Went Wrong with LAN Connection?
One of Wally ‘Larman’s commercial customers asked him to connect his newly installed DVR to his existing LAN so that he and others could remotely view the images being recorded. Wally obtained the necessary IP information from the IP Manager, ran a Cat 3 cable from the DVR to the LAN HUB and connected it as shown in this diagram. When Wally was finished the customer and his IP Manager were not satisfied. Can you see what Wally did wrong and what he must do to correct the problem?Answers to 20 Questions:
1. c – It is generally accepted that the human eye sees 30 frames per second as continuous motion.2. a
3. a – The NTSC standard uses 525 lines per frame and 30 frames per second.
4. a – The PAL standard uses 625 lines per frame and 25 frames per second.
5. b – IPCONFIG is the command used for Windows NT/2000/XP. WINIPCFG is used for Windows 95/98/ME.
6. b – Each DVR requires its own IP address to allow remote connection.
7. d
8. d
9. a
10. b
11. d
12. d
13. d
14. a – Remotely viewing video over a LAN can place a large burden on a network’s bandwidth, depending upon the number of viewing stations. For this reason some DVRs allow you to control how much bandwidth they will use.
15. b – An IP address consists of 4 octets separated by periods i.e. 999.999.999.999
16. d – Because the images are basically digital files they can be treated in the same manner as a standard image file.
17. d
18. c
19. b – Some DVRs are designed to connect directly to a multiplexer.
b – CDs do have a limited shelf life but, as with any technology, may be replaced with a newer recording medium that cannot read CDs.
Answer to: What Went Wrong with VCR Replacement?
Wally’s problem is caused by the T-taps he installed to connect the DVR. Using T-taps is not acceptable because it results in an impedance mismatch and adversely affects the quality of the video images. Wally should install a distribution amplifier as shown in this diagram and connect the coaxial cables for the DVR and multiplexer. As an alternative he could run the coaxial cable to the other multiplexer if it has available looping outputs. DVRs are more sensitive to low-quality video signals than traditional analog-VCR-based systems and may experience intermittent video loss problems if the levels are not correct. Installing the distribution amplifier will ensure that the video levels at the DVR are sufficient.
