About Spect
  • Explain about Digital Video Recorder (DVR)?
  • A Digital Video Recorder is similar to a VCR but records television data in digital format . Digital Video Recorders (DVR) encode video data in MPEG-2 or MPEG-4(Include H.264) formats and store the data in a hard drive. DVRs have all of the same functionality of VCRs (recording, playback, fast forwarding, rewinding, pausing).
    A DVR is essentially made up of two elements: the device that stores the hard disk drive and power supply, and some type of Electronic Programming Guide (EPG) that allows the user to program recordings.
    We can alsorefer it as a hard disk recorder (HDR) or a personal video recorder (PVR)

  • What features should I look for in a CCTV Digital Video Recorder (DVR)?
  • All DVRs are not the same! There are several factors that are critical to consider when purchasing a DVR. The most important factors to look at are the number of cameras supported, frames per second (fps), compression technology, hard drive space, network connection / remote viewing capability, motion detection, scheduling, and ability to save video and audio to a CD or flash drive.

  • What is frames per second?
  • The frames per second (fps) relates to how many pictures the DVR will record in a second. Real time recording is about 30 fps on each camera. To calculate the fps per camera take the total fps in the system and divide it by the number of video inputs. For example, a 60 fps digital video recorder with 4 video inputs would result in about 15 fps per camera.

  • How big a hard drive do I need?
  • The amount of hard drive space is very important because it will limit how many days of recording you can store before the system has to start recording over the oldest video. Each DVR will have its storage capacity listed in the specifications. But this calculation is just a rough estimate as there are many factors that affect hard drive use. But also the type of cameras that are connected to the DVR make a difference and also the features that are selected on the DVR. If you use the scheduling or motion detection features or tune down the frame rate that will extend the storage capacity of the unit. Even the field of view (what you are recording) will affect the storage capacity - the more complex the image, the more hard drive space it will take to capture the complexity.

  • How does a CCTV digital video recorder work?
  • A CCTV digital video recorder is essentially a computer that saves security video images to a hard drive. Most security cameras in use today capture an analog picture. The DVR converts the analog signal to digital and then compresses it.
    Many cameras can be connected to one DVR. DVRs generally come with 4, 8, 16, or 32 camera inputs. The DVR will allow you to view all of these images at once or one at a time, and all of the video is saved to the hard drive. Additional switches, quads, or multiplexors are not required.

  • Are security digital video recorders hard to install?
  • Not at all. You simply plug the cameras into the back of the unit. For the PC-based: Plug in the power, monitor, keyboard and mouse - just like a regular computer. You will receive instructions on how to set up the machine with your shipment.

  • How do I see pictures from a remote site?
  • You can view the camera video over the internet using a modem which is slow but can display 1 or 2 frames every 5 seconds. Better is a DSL or cable modem connection which can generally display 1 frame per second. When viewing remotely, the refresh rate is restricted by the communications medium (your internet connection speed). When viewing or playing back locally, the display is dependent of the unit's frame rate (fps). You will need a static ip address available to assign to the DVR

  • Which Security Camera Lens Should I Use?

  • How far you need to see will determine what security camera lens you should use to best fit your application. A 4mm lens will give about a 70 degree angle of view with 35 feet of facial detail. This works great for residential or small office security camera applications. If you need to see further you would go with a higher powered lens. Keep in mind that the further you want to see will narrow the field of view of your picture.
    A rule of thumb is that a 8mm lens is like a 4mm lens zoomed in 2 times. Similarily, a 16mm lens is like the 4mm lens zoomed in 4 times. For example, a 16mm lens would give you about a 15 degree angle of view focussed at 35 ft.

  • What If I Do Not Know Exactly How Far I Need To See?
  • Instead of going with a fixed focus lens you can go with a varifocal lens. With a simple adjustment you can manually zoom in or zoom out and focus the camera to the exact distance needed to get a clear picture. Varifocal lenses come in all different sizes: (3.5-8mm; 9-22mm; and 5-50mm) just to name a few. This is the best option for large commercial applications because you can adjust the focal distance to what works just right.

  • What is a PTZ camera?
  • A Pan Tilt Zoom camera (PTZ) allows you to pan (back and forth), tilt (up and down), and zoom (focus in and out) your camera remotely. The PTZ is controlled using a remote PTZ controller or you can control it through most DVRs (look for PTZ support). The disadvantages of a PTZ camera is that they are very expensive And all the moving parts make it susceptible to wear and breakdown.

  • What is the difference between no iris and auto iris?
  • The iris controls how much light is let into the camera lens. In the old days, cameras came with no iris control. If you needed to control the light levels you would have to purchase a special lens. Nowadays, most cameras come with automatic shutters which perform the same function as the iris - controlling how much light is let into the camera. Unless you have an application with extreme light levels (like at a beach) you probably won't need a special lens with iris control.

  • What is the difference between a static IP and a dynamic IP?
  • A static IP is a fixed IP address assigned to you by your internet provider that will never change. A dynamic IP is a constantly changing IP address that could change at any point.

  • What is DVRNS?
  • It is the DVR domain name server that you can login to the DVR remotely without typing in the IP address. For example if you name your DVR Securitall, you would type in the name Securitall instead of It is easier to remember a name instead of an IP address.

  • How does images per second affect the DVR HDD space?
  • The greater the images per second, the more disk space is used up when recording.

  • How does motion sensing and cameras work with the DVR?
  • DVR's detect motion by looking at the video pixels (little light and dark dots that make up the video picture) as the pixels change the DVR sees motion.  DVR's have a "Mask" or overlay for each camera, the screen is divided up into many small boxes called cells.  Each cell can be individually turned on or off to enable or disable motion detection in that cell.  This allows a camera not to see normally moving objects like trees or fans.  Each camera also has a sensitivity level setting that controls the amount of change in motion before the systems triggers.  All motion sensing is done in the DVR.  The camera has nothing to do with motion sensing, it just provides the video to the DVR.

  • Can I review recorded video and keep recording at the same time and not lose any recording time?
  • Yes

  • Can I switch from a split screen view (4, 8 or 16 cameras per screen) to a single camera view and keep recording all the cameras at the same time?
  • Yes

  • Can I record audio on my DVR?
  • Yes, as long as the camera has audio and the camera is connected to any of the first 4 ports on the DVR. Some states do not allow audio recording, make sure to check with your local authorities before recording audio.

  • How much time will a hard drive record for?
  • It depends on your DVR setup (Basic, High or Best) and your hard drive capacity. With the same hard drive capacity, setting DVR with High Quality image will shorten your recoding time. 160GB HDD on 4 Channel DVR with best quality image last for 1 week.

  • Can I view video from the DVR on my TV or do I need a monitor?
  • No, you can only use a CRT monitor or a VGA monitor

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