|
There are a vast range of CCTV products and prices to choose from in the
marketplace nowadays but only limited information to explain the difference
among them.
This brief guide helps you in deciding & selecting a suitable CCTV
security camera system.
Generally a CCTV security system must include at least the following
4 components:
- Cameras
- Display units
- Recording unit
- Connection parts & accessories
There are two types of CCTV cameras. CMOS and CCD.
CMOS cameras are generally cheaper but do not produce clear images
as CCD cameras do. CCD cameras provide pin-point clarity and should
be specified wherever possible, particularly when the price
difference between CCD & CMOS cameras becomes negligible, in terms
of total system cost.
We supply a vast range of CCD cameras, using only Sony sensors
(chipsets) to give best quality images.
These include:
Selection criteria of cameras: You need to consider the
following in choosing your cameras.
| Sensitivity
& Resolution |
Sensitivity reflects
camera's response to lighting levels & Resolution defines amount of
picture details in the image produced by cameras. Standard CCD cameras
give 380 TVL (Television Lines) while high resolution cameras can
produce up to 550 / 570 TVL for selective special applications |
| Indoor or
outdoor usage |
Outdoor cameras require
enclosures and weather resistance, strong aluminium housing and sealed
cable entry as well as vandal resistant structures are "must have"
features |
| Colour or
Monochrome |
A monochrome camera with 0.05
Lux produces reasonable quality images. A colour camera needs more and
can achieve better night-time vision by switching to a monochrome mode
automatically. However to get good night-time colour image, a huge
amount of additional lighting sources are essential |
| Day/night
operations |
True night vision cameras are
rated at 0 Lux and must include a ring of IR (Infra-Red) LEDs, offering
IR illumination. However as said, it will switch to monochrome at night
even with IR LEDS turned on, unless vast amount of lighting sources are
given |
|
Distance/length requirement |
You need to specify
the length of objects to be picked by cameras |
| Vandal &
security proof mechanism |
In some rough areas, an adequate
vandal resistant mechanism of cameras may be required |
| Wired or
wireless |
In most applications, wired
systems are preferred but in certain special environments wireless
cameras may be required. Under current legislation, maximum
allowable length of signal transmission is 100 metre in line of sight.
This will reduce to less than 30 metre when used indoors |
| Light
levels |
These are usually named in Lux which is a measure of the light energy arriving
on an area of one square metre of surface per second. This is probably the most
important factor to choose a camera to operate.
Typical light levels are:
| Full summer sunlight |
50,000 Lux |
| Normal
daylight |
10,000 Lux |
| Shop/Office areas |
500 Lux |
| Dawn/Dusk |
1 - 10 Lux |
| Main street lighting |
30 Lux |
| Side street
lighting |
0.5 - 3 Lux |
|
We recommend you choose cameras approximately 10
times it's quoted minimum scene illumination to guarantee quality and
meet your requirements. ( Top
)
Most CCTV systems deploy multiple sets of cameras using a video
switcher, a quad, or a multiplexer to view and record the images.
How to choose it, depends on individual needs and cost associated to
it:
|
Switcher |
|
Advantages |
simple to use, low
cost, good quality real-time images |
|
Disadvantages |
can record only one
camera at a time |
|
Quad Splitters |
|
Advantages |
simple to use &
shows multiple displays to monitoring several areas |
|
Disadvantages |
record only 1 camera
at a time or 4 at a quarter of the screen size |
|
Multiplexers |
|
Advantages |
record all camera
images full size, gives better monitoring simultaneously to
large areas without losing surveillance due to camera
switching time |
|
Disadvantages |
do not record in
real time and much more expensive |
Video Multiplexers
There are three functions of Video Multiplexers
|
Encoding |
taking a single
image from each camera in turn and feed it to a video
recorder in rapid succession |
|
Decoding |
playing back encoded
images showing only the selected camera for display |
|
Multi-screen |
showing live images
in different formats and can split screen up to 16 ways |
Types of Video Multiplexers
|
Simplex |
perform only one of the above functions at any one time |
|
Duplex |
perform any two of the above functions at any one time |
|
Triplex |
perform all three of the above functions at same time |
( Top )
Three ways of recording CCTV images:
| Domestic
VCRs |
This is the most
simple and low-cost solution. However a slow take-up time and can give a
maximum of 8 hours recording time are its disadvantages. |
| Time-Lapse
VCRs
|
Same to domestic
VCRs but with a slower-moving tape to record camera images as snapshots
at split second intervals. It can be set to give 24, 240, 960 hours of
recording on a standard VCR tape. It is a cost effective, long recording
method. However, the longer the recording time lasts, the longer the
period of time between the snapshots becomes its big disadvantages
|
DVR
(Digital Video Recorders)
Click
here to see our range |
Using a hard disc drive, a DVR takes analogue images from a CCTV camera,
digitizes & stores these images electronically for a longer period of
time. Generally there are two types of DVRs - Stand Alone and P.C. based
DVRs
Over the past few years DVR has become main stream recording choice for CCTV
security and will replace VCRs in the foreseeable future for most
applications. It has following advantages over the VCRs:
- All-in-one box for display, recording, multiplexing, alarms,
detection of motion and voice making installation of a CCTV system much
easier.
- Higher resolution than S-VHS VCR.
- Near instant access to recording time and date (unavailable from a VCR).
- Larger storage capacity reduces the need of frequent tape changes (Max.8
hours VCR).
- Enhance functions of playback, forward and reverse.
- Easy connection to LAN / Internet for remote viewing, recording,
playback etc.
- No loss of quality when copies taken
|
How to choose a DVR
We suggest you consider the following before selecting your
DVR:
| 1. Number
of channels |
Typical configurations are 1, 4, 8, 9, 16 channels (cameras). It is advisable to
purchase a little more then required, reserving room for expansion at a later
date.
|
|
2. Method of channel display |
A single channel DVR has limited functions.
A four channel DVR splits screen into 4 and display one camera
in each space.
A nine channel DVR provides a three by three (3 x 3) matrix display
of all channels.
A sixteen channel DVR gives a four by four (4 x 4) matrix
display of total channels.
|
|
3. Maximum frame rate |
Common DVRs specify 25 frames per second recording/display in total.
For high end system, you need a high Frame rate such as 100 FPS for
4 channels,
200 FPS for 8 channels or 400 FPS for 16 channels in total.
25 FPS/ per channel is a near real-time display / recording rate. |
|
4. Motion detection |
Most modern DVRs have a built-in motion detection system which
performs recording only when any motion objects are detected and
this triggers the recording process. It can stop unnecessary
continuous recording and prolong the duration of recording.
|
|
5. Duration of recording |
This depends on the capacity of your hard disc drive. The typical
setting allows your DVR to over write the oldest date / data and to
automatically start again at the beginning.
By using video compression technology and reducing number of images
per second, the capacity of storage can be increased.
Safe-Cores JPEG 2000 range of DVRs can tackle up to 10,000 hours
recording before the DVR starts to record from the beginning again
|
|
6. Remotely set-up, viewing, recording and monitoring
|
|
7. Retrieving and back up images recorded |
There are several ways of doing it.
- Remove hard disc drive and send to law enforcement dept
- Copy for the DVR onto a traditional VCR tape
- Send the image across a LAN or Internet
- Use a network connection to a P.C. with a CD / DVR
burner
- Built-in CD Writer
- Use USB memory sticker to copy & back up
|
We supply complete range of DVRs from basic entry level 1 channel / 4 channel to
16 channels cost effective & affordable DVRs to very high end, high
specifications versatile DVRs with up to 10 hard disc drive model which provides
up to 7,500 GB recording capacity for up to 200 days recording requirements.
Please view our DVRs range form the site.
P.C. based digital CCTV Systems
For those who have a P.C. already, simply add one of our
video-capture cards and a piece of surveillance software, they can
build a powerful CCTV surveillance system at affordable cost. Please
view our range of PC cards and PC based systems for details.
Over years we have already supplied vast stores of supermarket
chains, museums, race courts, shopping centres, broadcasting
companies, gasoline stations and commercial properties in the U.K.
P.C. based systems offer much more powerful features that Stand
Alone DVRs can do (please view our site to see all technical
details). However please note:
- Your P.C. hard drive must have sufficient free space to record the
camera images.
- Competence to install additional hardware and software.
- Have good housekeeping to ensure adequate free disc space.
- Have discipline not to use it for any other video capture or
editing or other applications.
(
Top )
Connecting images from cameras
to monitors, DVRs or TVs
The most common way in CCTV installation is to use BNC connectors.
The connectors twist and lock together giving secure connection to
cameras, monitors. You need to convert to phono or scart sockets if
you connect to a domestic TV or VCR.
Alternatively, you can use RJ45 composite cables/ connectors. A
simple adaptor is used to provide a BNC, Phono and a 2.1mm DC power
plug connector. This cable carries the video signal, audio and DC
power and is more flexible for installation in some awkward
locations.
Display images on CCTV monitors or TVs
The simplest way to display images from cameras is by connecting to
the AV input (or SCART socket input on a conventional
television). A simple BNC to Phono converter is all that
required to connect cameras fitted with a BNC type of connector.
Switchers, multiplexers and DVRs generally all have BNC input
connectors.
For more complex or sophisticated CCTV systems, a specialist CCTV
monitor (with higher resolution- more than 450 TV Lines) may be
used. CRT type or LCD screen monitors are commonly used for this
purpose.
We also supply VGA converter model
VC-101 to connect DVRs (without VGA output) to the CRT or
LCD monitors and delivers higher quality video footage than
conventional TVs can do.
If you require further technical details or expert advice, you can
ring us at 01952-204422.
( Top ) |
Login Status
