Video Surveillance Buyer's Guide

DVRs: digital video recorders for video security systems

Recording is essential to the effectiveness of any video security system. Without recording, you need to have an employee watching a monitor at all times - hardly a cost-effective solution. And even if you spot suspicious activity, without a recording, you have nothing to use in court.

All current video security systems include a digital video recorder (DVR) to store the images the cameras capture. In the past, the universal solution was the VCR. But with the introduction of digital video, capable of conveniently storing and organizing hundreds of hours of security footage, the cost-effectiveness of the tapeless technology has dramatically altered the landscape.

DVRs offer so many advantages over VCRs, they have completely taken over as the predominant CCTV recording medium:

• Ease of locating events- Instead of fast-forwarding through hours of tape, DVRs can instantly retrieve images from any specific time or date, or automatically skip to the point on a recording when something changed.
• Storage quality- Video cassettes start deteriorating almost immediately once you record on them - and the resolution gets worse every time you reuse them. DVR recordings have no degradation at all since they are stored onto a hard drive.
• Multitasking- While analog VCRs can either record or play, DVRs can do both at the same time, letting you review images while still recording.
• Smart monitoring- The DVR can be set to take one picture per second or less - just enough to create a running record for weeks or even months. However when it detects motion, it can automatically bump the recording speed up to full (30 frames per second), capturing every detail of the activity.

Choosing a DVR

There is no magic number or spec here: you need to decide how "good" the recorded picture needs to be, either for your own use later or possibly for use in court. Vendors may be eager to throw compression settings, pixel counts, and other statistics at you - but those numbers are irrelevant if the picture itself does not offer the detail you need for legal or investigatory purposes.

The size of the hard drive will dictate how much you can record. On the low end, a 500-gigabyte (GB) hard drive will store about 500 hours of full-motion video from one camera. Units expand up to 3 terabytes (3,000 GB) and can store up to 16 channels (or cameras) worth of data over extended periods of time. Also keep in mind: digital files are much easier to store than VHS tapes or even DVDs, transferred in minutes to an external or internal backup hard drive. In doing so, you can quickly free up space on your DVR.

Supplementary internal hard drives are a cheap way to boost storage capacity. With some DVRs, you can buy additional 500 GB hard drives for as little as $60 and 3 TB models for $175 to $250, swapping them in and out as needed.

Another consideration is how many cameras you want to connect to the DVR. Keeping potential expansion in mind, buying a higher-grade model to get more inputs and more storage space can save you considerable money in the future. The DVR will also function as a multiplexer, putting up to 16 cameras on one display and allowing operators to call up any one image for closer inspection.

Plus, with the growing popularity of IP connectivity, many models can be tapped into through your laptop, iPhone, Blackberry or Windows mobile device, allowing instant access and monitoring from any location.

Finally, if you ever have to use your security images – in court or otherwise – you'll need to be able to export the video. This is an important consideration: most high-end systems record video and images in industry-standard MPEG4 and JPEG files, which can be streamed through the web and played on any PC. They can also be burned onto a CD-RW or DVD-RW disc for viewing on any DVD or Blu-ray player. So when purchasing a system, make it offers some form of video export.