- Technical Blog From My Notebook

Thursday, December 3, 2015

Television (TV) Basics

Television
  • Tele- vision- To see from a distance
  • First demonstration -J.L. Baird in UK and C.F. Jenkins in USA around 1927
  •  Technique of mechanical scanning employing rotating discs
  • CRT- Cathode Ray Tube
  • First camera tube (the iconoscope)
  • 1930- electromagnetic scanning of both camera and picture tubes and other ancillary circuits

The fundamental aim of a television system is to extend the sense of sight beyond its natural limits, along with the sound associated with the scene being televised. In most television systems, as also in the C.C.I.R. 625 line monochrome system adopted by India, the picture signal is amplitude modulated and sound signal frequency modulated before transmission. The carrier frequencies are suitably spaced and the modulated outputs radiated through a common antenna. Thus each broadcasting station can have its own carrier frequency and the receiver can then be tuned to select any desired station. Figure 1 shows a simplified block representation of a TV transmitter and receiver.

Television Systems
In the absence of any international standards, three monochrome systems grew independently.
1.      525 line American
2.       625 line European
3.       819 line French systems
Three monochrome systems
1.      National Television Systems Committee (NTSC)system.
2.      PAL ( Phase Alternating Line)
3.      SECAM( Sequential couleur Avec Memoire) 
      Applications of Television
·         Public entertainment
·          Social education
·          Mass communication
·          News casts
·          Weather reports
·          Political organization and campaigns
·          Announcements and guidance at public places like airport terminals,
·         Sales promotion
·         Closed Circuit Television (CCTV) camera signals are made available over cable circuits only to specified destinations
·         Special type of CCTV -wired community TV- (Small communities
That fall in the ‘shadow’ of tall geographical features like hills can jointly put up an antenna at
A suitable altitude and distribute the programme to the subscribers’ premises through cable circuits
·         Video-telephone or ‘visiphone’.
Equipment
Television broadcasting requires a collection of sophisticated equipment, instruments and
Components that require well trained personnel.
Television studios employ ;
  • Extensive lighting facilities
  • Cameras
  •  Microphones,
  •   Control equipment.
  • Transmitting equipment for Modulation,Amplification And radiation of the signals at the high frequencies used for television.
  • Support equipment essential in broadcast studios, control rooms and outside includes
  • Video tape recorders,
  • Telecine machines,
  • Special effects equipment +all the apparatus for high quality sound broadcast. 


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