•   What is Digital CCTV?
•   Guide to Analogue CCTV
•   Guide to Digital CCTV
•   Guide to Digital Video Recorders
•   Guide to PC Based Digital Surveillance Cards
•   How to choose a Digital CCTV Camera & Lens
•   CCTV Glossary

What is Digital CCTV?  
    Digital CCTV, or Digital Closed Circuit Television, is the technology used in modern surveillance systems. Traditional ,VCR, CCTV pictures are sent via cctv cameras to a closed area, e.g. a CCTV Monitor, this type of CCTV is likely to produce lower resolution images and have to be displayed via cabling in the workplace. Modern Digital CCTV Systems can be operated remotely via a pc or mobile phone, can monitor various locations and can be monitored from wherever there is internet or GPRS Access.

A History of CCTV Systems
The saving of CCTV footage has changed in the last 5 years. The industry move has been away from analogue to Digital CCTV Systems:

Analogue CCTV
    In the past, all CCTV Cameras were attached to a Multiplexor (A device that will split multiple camera pictures onto an individual CCTV Monitor). The Multiplexor then sends the analogue camera images to a Time Lapse Video Player. These are special CCTV recording devices that can record up to 960 hours of footage on a three hour Video Cassette. This method is still used today for simple CCTV installations but the quality of recording is usually very low (1 Frame Per 12.8 Seconds).

Digital CCTV
   Currently the majority of CCTV systems use Digital technology. Digital CCTV Surveillance uses current PC technology to digitize the CCTV camera images and compress them into a PC friendly format. These digital images can then be stored on a PC's Hard Disk Drive. As the digital cctv images are stored on a computers Hard Drive it is possible save digital cctv footage and access it speedily and easily. Digital CCTV also has the advantage over Analogue CCTV systems that the image are of a far higher resolution.

There are two types of Digital Surveillance Systems:

Digital Video Recorders
    A Digital CCTV Video Recorders, (DVR's), are stand-alone units that are capable of saving digital CCTV images to a PC. DVR's look similar to a standard Video Cassette Recorders (VCR's).

CCTV Cameras are connected to the back of the unit via standard CCTV Camera connection referred to as BNC. By connecting a CCTV Monitor or standard Television to the DVR you are able to view your CCTV Cameras in different screen divisions (single camera, 2x2,3x3 etc) and also playback footage at the touch of a button.

Some DVR's can have built in Motion Detection Technology. This means that digital footage is only recorded when someone or something walks in front of your CCTV Camera.

It is also possible with some DVR's to view your cameras remotely via an ADSL (Asymmetric Digital Subscriber Line).

PC Based Digital Video Surveillance Capture Cards
    PC Based Digital CCTV Surveillance systems are a reasonably new technology in the CCTV Industry. This type of Digital CCTV system works in two stages. You then install the digital cctv surveillance card and software on to your PC. This Software (or program) will allow you to view your Digital CCTV Cameras, search through previously recorded footage, backup footage to CD/DVD, control PTZ Cameras either on the PC system or remotely and much much more.

Cameras are attached to the back of the Geovision PCI Card using the standard BNC connection used in all CCTV Cameras.

Geovision Surveillance cards come in a variety of formats depending on 1) The amount of cameras required (2-16)
2) The Frame Rate per Second (FPS) Quality required (16 FPS - 400 FPS)

Frame Rate is important, as the higher the Frame Rate, the higher the quality of recording and the more Real Time your cctv recording will be.

Real Time Recording for 1 camera is 25 Frames Per Second (PAL). In order to capture 16 cameras in Real Time, you would need:

25 FPS x 16 Cameras = 400 Frames Per Second PCI Surveillance Card

How to choose a CCTV Camera & Lens?
    Choosing the correct CCTV Camera for your digital surveillance system is very important. The Digital CCTV Camera, together with a CCTV Lens, uses a CCD (Charge Coupled Device) sensor that captures the image and turns it into a signal that is sent to the monitor or surveillance system.

You will need to decide the following when choosing a cctv camera & lens for a digital cctv system:

The Digital Camera Location : Will the camera be situated Indoors / Outdoors

The amount or variance of light conditions for the digital cctv camera : Will the camera have to record in low-light conditions such as at night?

The Field of View required for the camera : How wide or narrow an angle of vision is required

The Focal Length
How far away objects you wish to record will be from the camera

Your budget

If you would like help on choosing a Digital CCTV Camera Lens visit the
Digital CCTV Camera Lens Help Page.