CCTV Buyers Guide....

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

Outdoor cameras require enclosures and weather resistance, strong aluminium housing and sealed cable entry as well as vandal resistant structures are "must have" features

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

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

You need to specify the length of objects to be picked by cameras

In some rough areas, an adequate vandal resistant mechanism of cameras may be required

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

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:

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.

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

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

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.

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.

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.

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.

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

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