Welcome to the

"History of CCTV" Section
of
Doktor Jons
Guide to Closed Circuit TV (CCTV)

<< The faceplates of 2/3" 'Vidicon' camera tubes - circa 1980

A potted history of CCTV - continued

Whilst a few European cities experimented with using cameras for traffic control, the residential use of CCTV was simply restricted to those wealthiest individuals, with the biggest properties. Of course, as the scale and pattern of criminal behaviour has accelerated over the last twenty years or so, there has been an ever growing demand for visual surveillance throughout practically every aspect of modern life.

In response to spiralling crime, successive UK governments have over the last ten years, pumped hugh sums of public funding into encouraging the widespread adoption of public area CCTV. So much so, that the United Kingdom is now ‘guesstimated’ to have perhaps three to four (or more!) million Closed Circuit TV cameras in use, and questionably claims its ranking as the CCTV capital of the world. As with most things in life, quantity doesn’t always equate to quality, so if you browse through other areas of this site, you’ll quickly get a much better idea as to why Doktor Jon considers, there is still so much room for improvement.

In the meantime, let’s take a very brief look at the modern development of Closed Circuit Television.

< 2/3" and 1" 'Vidicon' camera tubes

The photograph shows (l. to r.) an electrostatic Toshiba 2/3" tube, 1" Siemens electromagnetic and 2/3" RCA electromagnetic tubes, all used in various model Black and White surveillance cameras, during the 1970's.

The expected centre of image resolution figures for each would be in the order of 550 lines, 750 lines and 600 lines respectively, with sensitivity at best down to perhaps 5 - 10 lux.

The tubes would wear with age, and estimates of life span varied from 2 - 5 years on average, depending on the application and camera set up. That said, under ideal conditions they could last a lot longer

In the mid to late 1970’s, all CCTV cameras were built around a now outdated device, the 'thermionic valve' (the same technology as was used in early radio & TV sets.). The principle was that an imager (in this case a glass vacuum camera tube - see photo above) was held securely in a large magnetic coil, which in turn controlled a scanning beam of electrons used to 'release' the image.

The inverted image produced by the lens was then brought into sharp focus on the front ‘face’ of the tube, which itself incorporated a special chemical layer, protected behind the flat glass ‘faceplate’.

In very simple terms, this chemical layer would convert the image into a low level electrical signal, which is then amplified and processed into a displayable video signal.

Continued>

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