CCTV

Frequently Asked Questions

Are all cameras the same?

No. There are many different types of CCTV cameras. Monochrome (Black & White) and colour are the obvious differences but there are also low and high resolution. Higher resolution cameras produce a much sharper picture but are more expensive. Most CCTV installations now use colour cameras as the costs have fallen, but Monochrome cameras are still used for low budget systems or for night time use where Infrared lighting is required. There are now even cameras that are colour during the day and change to Monochrome at night.

Where can cameras be fitted?

A CCTV camera can be installed just about anywhere but care does need to be taken that privacy is not invaded. Cameras can be fitted internally on brackets or externally in weatherproof housings. Powerful lenses can be fitted to enable distant objects to be viewed in detail.

I have heard about hidden cameras what are they?

Covert or hidden cameras are small CCTV cameras that can be fitted inside everyday items such as clocks or fitted above false ceilings. These are often used to detect fraud or theft and can secretly record people's actions. As most covert CCTV systems are only required for short periods of time

Not all lenses are the same, why is that?

Some of the most important parts of any CCTV system are the lenses. These come in many different designs suitable for any application. The main types of lens are the 'fixed iris', 'auto iris', and 'fixed focus' or 'zoom'. A 'fixed iris; lens will have the light level set during the installation but will automatically adjust varying to brightness levels.

The difference between 'fixed' or 'zoom' lenses is quite simple. The 'fixed focus' lens is set up and focused during installation. The 'zoom lens' can be adjusted by the user to move closer or farther from the object.

There are two important rules to remember with lenses:

1. They can only focus on one point at any moment in time.

2. The larger the viewing area the lower the detail and vice-versa.

What about recording pictures?

Most CCTV systems will use a VCR to record the images. These differ from the VCR found in the home because they are designed to operate 24 hours a day, every day of the year. The VCR also runs a lot slower and can make a standard 3 hour VHS tape last over a month. Usually though this is a 24 hour time period. As a result there is far more wear on the tape and it is recommended that the tape is not used more than twelve times at 24 hour rate.

Other methods are available, Super VHS is the most common and more recently digital recorders are being introduced. Pictures can also be sent via telephone lines and recorded remotely. Recording onto DVD will also be available in the future. The great advantage with digital recording is that the pictures can be re-recorded many times without loss of quality and special events can be indexed for rapid playback. Also with today's technology these pictures can be sent to anyone with a compatible computer via e-mail or the Internet.

How do you record more than one camera with one video?

This is done in one of two ways, firstly a switcher; this is a device to which all the cameras are connected and has one output to the VCR. The switcher will sequence through the pictures one by one. The VCR will record only the camera showing on the monitor. A switcher is only suitable for small numbers of cameras.

The second method is a Multiplexer. This is a device that digitally encodes all the cameras and records them frame by frame. This gives the effect that all the cameras are recording simultaneously. Multiplexers come in all shapes and sizes and can have from four to sixteen cameras connected, some also allow multi-screen (more than one camera) pictures while recording.

Can a camera look at more than one area?

Yes. The main reason for wanting to do this would be to get a more detailed view of a larger area. There are units which can move cameras, these can be as simple as left to right 'panning' motion or as complex as a fully controllable 'PTZ' (Pan Tilt Zoom, a camera which can be moved in all directions and zoomed in and out). It is important to remember with CCTV cameras that the greater the viewing area the lower the detail and vice-versa.

Another advantage with panning or PTZ cameras is that a large area can be covered with fewer cameras reducing installation costs.

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More information:

CCTV FAQ

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