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Choosing The Right Security DVR

Security DVRThere are many factors that go into choosing the right DVR (digital video recorder) that must be decided before purchasing. To start with, you will want to consider how many channels you will need. Each channel is a camera input and most DVRs come with 4, 8, 9, or 16. While there are DVRs that only have a single input, for the purposes of this discussion, we are assuming you are looking for a multi-camera setup.

With a basic 4 channel setup, you can usually cover a good amount of area by choosing wider angled cameras, however, you may not want to limit yourself to only getting 4 cameras. By choosing an 8 channel DVR you allow yourself some room to expand in the future. This can extremely beneficial if you find that there are too many blind spots in your 4 camera setup as you just need to get some more cameras. A good rule of thumb then is to walk the perimeter of the areas you want covered and check to see roughly how many cameras would be required for the minimum setup. For example: You know you have to cover the front and rear entrances, but you also need a camera pointed at a cash register. Your basic requirements are for 3 cameras. Once you know that, you then want to check for any possible areas that might be considered high traffic or desirable. A display cabinet might be overlooked on initial glance, but if you find that the cabinet gets a lot of attention, you may want to point a camera in that direction too. Going back to our example, your basic requirements are now up to 4 but you still may need more cameras. Having more channels available therefore can be of great benefit, but also consider that having too many can be a problem as well. If you are setting up a security system in a small office, you may not ever need more than 4 cameras so getting an 8 or even 16 channel DVR is a waste of money. Your PolarisUSA sales rep can help in making the right choice.

Hard Disk Secondly, the size of the hard drive comes into play. While it is impossible to say exactly how much time you can record with any given hard drive, you can estimate that at maximum settings with a typical DVR you get about 1 hour per channel per gigabyte. So with a 16 channel DVR you are using 16 gigs per hour with the highest settings. By lowering the resolution, recording only on motion, or lowering the frame rate you can greatly increase the amount of time recorded allowing you to get a week or even a month’s worth of video before it begins to record over itself. The other advantage of motion detection recording is you no longer need to spend wasted time watching countless hours of useless video waiting to see if something happened. It gives you a time and date stamp of when something occurred and you can go right to the event, whether it’s a bird flying by or someone scoping out the place. This feature alone is the most impressive and useful for just that reason. The last to note about hard drives are the differences between Serial ATA (SATA) and Parallel ATA (PATA). Many DVRs are making the switch to SATA, which is the current most popular standard. SATA drives are less expensive and available in larger capacities. PATA will become obsolete before long, so you're better off with a SATA-compatible DVR.  A lot of DVRs have 2 hard drive bays or more, so you can get multi-TB capacity -  perfect for anyone looking to store very large amounts of video.

CAT5 Cable The next deciding factor becomes networkability. A lot of the current DVRs are set up to be accessible remotely so you will want to think about whether or not you want to be able to see the cameras from another office, or home or perform remote backups. This also means you won’t need to purchase additional monitors to be able to view all of the cameras, instead, each PC workstation can just access it on their individual computers.

Going into the numerous features that are left would take up volumes so we will hit briefly on some of the more important aspects here. Let’s begin with audio. Some cameras have built-in mics or you can use external microphones for those that don’t, provided your DVR handles audio. Most will support anywhere from 1-4 channels of audio, usually correlating to that numbered camera, i.e. channel one of video is linked with channel 1 of audio and so forth. While it is possible to find a DVR with 16 channels of audio, it is rare. Covert audio recording is illegal in most states and as a result, this feature is not widely used. Offloading video is the next item to discuss. Some DVRs have built-in CD or DVD burners and others use a USB port to offload the data to a flash drive. With the current capacities available in flash media, CD/DVD burners are generally considered obsolete for DVR exporting. Something else to consider when choosing which DVR to go with is the Images Per Second (IPS). The IPS is usually given as the combined total of all channels. Real Time is considered 30 IPS per channel. When looking for a DVR, you will see them noted as having, say 120 IPS for an 8 channel DVR. By dividing the number of channels by the IPS you know that you have a maximum recording rate of 15 IPS or half speed. Be aware of advertisers trying to confuse you with Live View Images versus Recorded Images. Keep in mind that you are not skipping or losing time, you are just recording less frames each second. This makes the video less fluid but saves hard drive space and increases the recording time. Real Time DVRs are usually more expensive and often unnecessary.

Each output on the bottom row is simply a pass-through for each input on the top row.
Next on the list is looping video. This is simply a video pass through for each channel. If you have a guard station that only needs to see the front door on a monitor, you can use the loop feature of a DVR to only have that one camera go to a separate monitor. All of the cameras are still viewable by the main monitor, you just get an additional feed of that one particular camera. After that, most DVRs will have RS-485, VGA output, and alarm inputs/ outputs. With some DVRs it is important to note the VGA might be an upgrade so if you plan on providing your own monitor using a VGA port, make sure the DVR you choose has it available or that you opt for the upgrade. The RS-485 interface is for using PTZ cameras and it is vitally important that you know the protocol of the camera you are using. Some manufacturers use a proprietary protocol that may not match up with your DVR. Fortunately, most DVRs and PTZ cameras use the Pelco-D protocol, but it is always a good idea to double check beforehand. Alarm inputs and outputs can control and monitor devices such as door sensors, passive infrared (PIR)sensors, smoke detectors, etc. These in/outputs are handy for vacation homes or companies to monitor the status of various sensors.

Alarm I/O

You now have the ability to make an informed choice but there will always be something new on the horizon. Watch this blog for any future news on the current trends of the CCTV industry.

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Submitted by Tony M. - 10/15/2008 @5:26pm

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21518 Views      |      2 Comments Post Comment
Submitted by nick - 10/13/2012 7:04:55 PM
Thanks alot for the helpful information! I will purchase my future survailence cameras from Polaris USA.
Submitted by JJMaddog - 08/24/2009 9:23:30 PM
Thank you that answered alot of questions.

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