A Basic Guide to CCTV – Analogue CCTV or Digital CCTV?


There is a lot of mystique about security and security systems which is unhelpful if you are in the business of either buying or managing one.  This guide will hopefully explode some of the myths that abound, delivering some clarity.

The starting point for most people is understanding the difference between a digital and analogue system and how they work.

It is worth noting that the cameras and recording devices all look the same or at least so similar that to the untrained eye, there is no difference.  When viewing a monitor, most people prefer a digital system, something exacerbated by most analogue systems being dated.

There is no question that the areas where analogue held a clear advantage such as low light situations and where fluorescent lighting was in operation have been addressed by the new digital cameras, in essence we live in a digital era meaning that analogue systems are being phased out and for some manufacturers, no longer produced.


Analogue CCTV Overview

That said, if you current own a digital system how is it made up?

An Analogue system comprises of a camera(s) fitted with a CCD (charge-coupled device) chip that digitises the light it picks up capturing the image for processing. To enable the image to be sent to the video monitor or recorder, the image is converted back to an analogue signal that is NTSC/PAL compliant.

To help with comparisons, it is worth noting that the maximum resolution allowed by the NTSC/PAL is equivalent to 0.3 megapixels.

If your system is particularly old you may have videotapes that require frequent changing.  It is more likely that your system has a Digital Video Recorder (DVR) where the digitized video images are stored.  The images are stored on a hard driver typically on a FIFO (first on, first off) basis so that there is always a rolling video archive over a user defined number of days.

30 days became the standard recording requirement given that most companies had a line of 31 tapes close to their recorder to correspond with the number of days in the month.  The size of the HDD (hard disk drive) does not necessarily give a good indication on the number of days recording you should expect.  The quality of the image coupled with the frame rate dictate the size of the HDD needed, along with the number of cameras involved.

Digital System Overview

A digital system is often referred to as an “IP” one, “IP” standing for the Internet Protocol which is the low-level programming language used to transmit data between computers.  In essence an IP camera is like a little computer that can be placed anywhere on a network and accessed remotely at any time.

IP systems do not require a DVR and instead use an NVR (network video recorder) which can either be software (VMS) running on a computer/server or a standalone unit.

There is no need to convert analogue signals to digital with images stored on a new or existing network RAID (redundant array of independent disks) drives as directed by the NVR software.

A key difference between the two systems is the IP cameras ability to capture high definition, megapixel images.  With each camera being effectively its own little computer, it can perform a number of advanced functions from detecting motion through to trigger recording.

Depending on the system and how it is set up, images can be emailed, stored on an internal storage card or transmitted to an external storage device.



We’re answering Frequently Asked Questions about CCTV Security over on our next blog. Click here to read.