From analog systems to cable TV and after, drawing rooms the world over today boast of Plasma TV sets, DTH (direct-to-home), Digital Satellite Systems (DSS), and HDTV (high definition television). This has been made possible through the communication technology revolution that kept pace with the digital advances in computer and Information Technology particularly in the last few decades.
When transmission on television first began between the year 1928 and 1935, the quality of picture details were so small and unclear that the system was called as "low definition". This was because a picture would be made of only about 30 lines, and hundreds of such lines would be required to give a picture with some resolution. Technology improved with the maiden "high definition" system brought out by the "BBC" in the year 1936. (Berry 2005). This was composed of 405 lines. An improved version with relatively better picture clarity (625 lines) emerged in the year 1964).
The basic television technology involved the transmission, capture, and reproduction of a picture by the receiver unit known as the television set. A picture tube or CRT (cathode ray tube) consisting of an electron beam was used for this purpose. The screen with uniform phosphor coating would emit light when the electron beam struck it. The images that we see on the TV screen, called pixels, basically consists of small rectangular dots. Every pixel is made up of three closely compact dots having the colors of blue, green, and red. The early images were transmitted and reproduced in black and white. Color television emerged by the technology of converting the black and white dots into color. This was done by breaking the dots into the three basic color shades. The resolution of pictures on television screens was improved by using smaller pixels compacted more closely together. This technology gave rise to High Definition TVs (HDTVs) that are being increasingly used today.
Analogue vs. Digital
The earlier versions of television depended upon the analogue mode of transmission. Analogue as well as digital signals both tend to become weak as they travel greater distances. Better picture resolution is normally possible only with strong signals. If the analogue signal were weak, the quality and resolution of the picture would be poor. On the other hand, in case of digital transmission, the picture quality would remain perfect as such so long as the television can keep receiving the signals.
For the purpose of transmission and broadcast of more high definition pictures, it became necessary increase the bandwidth or to compress the data load. Digital signals have the capability for greater compression, while analogue signals have limited scope in this aspect, as every pixel needs to be included for transmitting an image on analogue television. (PBS Online 2005). Video can be easily compressed for digital TV by using the MPEG-2 method. This system uses frames and encoder to compress visuals by registering changes in the image. The compression technology offered by MPEG-2 is increasingly being used in digital DVD videos and satellite TV, apart from digital TV. However, this method suffers from the possibility of a loss in picture clarity in case of a very high compression