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CCTV - A Guide To CCTV Equipment And Closed Circuit Television Monitoring


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What is CCTV?

CCTV, or Closed Circuit Television, is not a new invention. Unlike your home TV where programmes you watch are probably being viewed by millions of people all over the country, known as Open Circuit Television or OCTV, a closed circuit system is one where the signal is linked directly from the source – in this case a surveillance camera – to one display device. The signal cannot be intercepted and viewed by an outsider, hence the ‘closed circuit’.

CCTV has been widely used for decades as a way to monitor everything from bank safes to prison convicts, and is a common tool for businesses and even homeowners to keep an eye on what’s happening on and around their property.

 

About DVR

A DVR or Digital Video Recorder is essentially a hard drive designed to store the footage that the cameras are capturing, so that it can be re-played later if needed. Without a DVR you’ll be able to watch what’s going on in real-time, but in case of a burglary for example you will have no recorded proof to show the police as evidence, which is why a DVR is such an essential piece of equipment to go alongside your CCTV system.

Some key factors to consider when choosing which DVR to buy are:

 

Choosing a CCTV Monitor

There is a multitude of different monitors to choose from when it comes to setting up your CCTV system, so be sure to take these 7 factors into consideration to ensure you’re choosing the best one for your needs:

  1. To reduce and resist electromagnetic radiation, which could interfere with the CCTV system’s functionality, opt for metal rather than plastic cased monitors
  2. CRT monitors will generate a lot of internal heat and need to be in an area with good ventilation to avoid damage from overheating.
  3. Another important thing to take note of regarding CRT monitors is that you can’t leave the same image on screen for any length of time – i.e. pausing it – as this will burn the image into the phosphor coating of the tubes and you won’t be able to get rid of it. This is why old, bulky computers commonly had moving screensavers!
  4. A multi-standard PAL / SECAM / NTSC unit can be used to play back footage using a suitable player.
  5. Flat screen monitors provide a host of advantages over CRT tube monitors but are higher in price.

 

Choosing a CCTV Camera

You have the choice of a mono, colour or colour/mono CCTV camera, which each have their advantages. Mono cameras are only able to capture images in black and white, but are the cheapest option and ideal for those on a budget. Colour CCTV cameras are better for use as evidence as they will display a full colour image, making it easier to identify people or objects in the image. For example, you will be able to see the hair colour and clothing colour of a suspect in a robbery. Colour/mono cameras however are able to capture full colour images during the day and then monochrome images at night when a standard colour camera would struggle to capture anything.

Once you’ve decided on the correct camera type for your needs, also consider the following points:

Illumination

Example

0.00005 LUX

Starlight

<1 LUX

Moonlight

10 LUX

Candle at a Distance of 30cm

400 LUX

Sunrise or Sunset on a Clear Day / A Brightly Lit Office

1000 LUX

Typical TV Studio Lighting

32000 LUX

Sunlight on an Average Day (Min.)

100000 LUX

Sunlight on an Average Day (Max.)

 


Choosing a Lens

The lens you choose will determine the view your camera can achieve. A longer focal length will give a narrower angle but can see items further away more clearly, so you need to weigh up the options and find a good compromise between angle and distance.

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The two main types of lenses are fixed focal lenses and vari-focal ones. A vari-focal lens has an adjustable aperture, for example between 5 and 12mm, allowing you to zoom in if needed.

You also need to choose between a fixed, manual or auto iris. The iris of the lens determines how much light gets in – a fixed iris always lets the same amount in so whilst cheap it may mean that on bright days the image is too bright to see properly. A manual iris allows you to change this yourself, whilst an auto iris will increase or decrease the amount of light it is letting in automatically for the best picture brightness at all times.

 

Choosing a Power Supply

Each camera has its own level of power required. Most of the cameras stocked at Alert Electrical require a 12V DC power supply but some have built in 12/24V adapters and others need 230V AC power to function. High voltage 230V cameras required a qualified electrician to connect them to the mains so if you want to install the camera yourself opt for a 12V DC camera. It is important not to supply the camera with more voltage than it is rated for as it will simply blow the board and render the camera useless. You can however over-supply amps as the camera will only take what it needs.

A 12V or 24V camera requires a special power supply to convert the 230V mains power to the appropriate level. A power supply unit, or PSU, is available as individual plug-in units up to 1 Amp for single cameras, or metal boxed power supplies up to 3 Amps for multiple cameras. For example, a CCTV system with 8 12V cameras consuming 0.2 Amps each would require at least 1.6 Amps from the power supply.


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