Digital
CCTV Help
If
you are new to Digital (Closed Circuit Television) CCTV Security
and need some more information, please see below for our guide to CCTV
products and terms.
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
How
to choose a Digital CCTV Lens
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.
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 DVR PCI Card using the
standard BNC connection used in all CCTV Cameras.
DVR 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?
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:
1.
The Digital Camera Location : Will the
camera be situated Indoors / Outdoors
2.
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?
3.
The Field of View required for the camera :
How wide or narrow an angle of vision is required
4.
The Focal Length
How far away objects you wish to record will be from the camera
|
