Applications and opportunities for video have gone through a revolution in recent times, owing to advances in technology and a heightened demand for security and surveillance in our society.
The term “CCTV” (closed circuit television) was originally a phrase used to differentiate dedicated video surveillance hardware and systems from those designed and used for broadcast applications. It is still used to describe a broad range of equipment and applications.
All television technology was based on vacuum tubes and analog transmission and processing. Cameras utilized vacuum tubes to sense images, convert the signals for transmission, receive signals, convert them for display, amplify the signals and display the signals. I am not sure, but I imagine tubes were even used in early video recorders, although my own recollections only go back as far as videocassette recorders using transistor technology. Videocassettes are just magnetic tape housed in a handy container.
The technology transformation began with the introduction of transistors. The transistor took us across the threshold into the realm of “solid state.” Your floor model radio now could fit in your shirt pocket.
The milestone in video technology was the introduction of the solid-state image grabber, The Charge-Coupled-Device, which replaced the vacuum tube vidicon tube. Vidicon tubes had a host of problems, which became intolerable as soon as the benefits and advantages of the solid-state image grabber were revealed and refined.
The milestone in video acceptance was the fact that there was soon to be television in every home, and they broadcast images that were captured by cameras.
Vidicons were delicate apparatus with filaments and complex architecture. They used a light-sensitive coating that deteriorated over time. CCDs lasted longer and were far more robust.
Vidicon used a lot of power; requiring filament AC voltage as well as high DC voltage. This meant a lot of weight and bulk in the camera, and again sensitivity to a variety of things such as temperature and vibration. Vidicons had a finite lifespan and they also died slowly. From the moment the Vidicon was first powered up, it began to wear out, and the image quality began to deteriorate. Service and performance issues were complex.
The CCD was light and rugged, and generally speaking, it either worked or it didn’t. It weighed comparatively little and used only low voltage DC. CCDs were rated in terms of their light sensitivity and resolution, so the correct Vidicon could be specified for the application, and the performance of the CCD would be predictable and consistent.
Concurrent with the revolutionary introduction of the CCD, was the rapid development of computer technology, networks and the Internet.
The New Video
You can call it CCTV if you want, but it’s more accurate to refer to this realm as New Video. The industry has gone totally digital. The cameras use digital image grabbers and signal processors and communicate via digital network protocols over wire or RF. The images are processed via digital signal processing techniques using both off the shelf PCs and proprietary hardware. Image storage is on hard drives.
Transmission lines, once primarily coaxial cable, are now networks, the Internet or RF links. Recording and archiving of video can be full time so that advanced techniques are at even small video system users' fingertips.
For example, consider pre-alarm recording. With VCRs, image storage capability was a limiting factor. If a cassette ran out of room, then either the recording process stopped until the cassette was manually replaced, the recording process was interrupted while the VCR rewound the cassette and began recording over the cassette, or in high-end sophisticated set-up, the first VCR would sense that its cassette was full, and automatically switch recording to the next cassette recorder. Cascading VCRs was an expensive, complicated and failure-prone set up.
Digital video delivers improved quality, which enables more details and changes in images.
Shipped in a single box with the camera and lens already mounted in the enclosure, “plug-and-play” packages from a single manufacturer simplify installation as well as the ordering process...