Securit Camera

Discussion in 'Homework Help' started by Nirvana, May 24, 2005.

  1. Nirvana

    Thread Starter Well-Known Member

    Jan 18, 2005
    58
    0
    Hi if the specifications for the security camera says :

    Resolution: 470 TV Lines



    Doesthis mean the output signal can be used in 470 televisions, can we see what the camera sees in 470 different televisions???

    Please Help
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Televisions, at least in the pre-digital days, painted the picture on the screen as sequence of horizontal lines on a CRT (cathode ray tube). In 1/60th of a second, it would paint 262.5 horizontal lines starting at the top of the screen and proceeding to the bottom of the screen and the next 1/60th of a second it would paint 262.5 horizontal lines interleaved between the previous 262.5 lines. These 525 lines made up 1/30th of a second of the picture. The analog cameras were designed to be compatible with this convention.

    I should point at that this description is based on the NTSC (National Television Standards Convention) standard prevalent in the USA. In England and Europe, the PAL (Phase Alternating Line) is the prevailing method of TV broadcast. The PAL stanadrd uses 625 horizontal lines instead of the 525 lines.

    I think this reference to the 470 lines of resolution is a hold over from this convention. It means that the scene being captured by the camera is being divided up into the equivalent of 470 lines along the vertical axis.

    Digital television still updates the screen as horizontal lines but the days of analog CRT based televison and cameras is rapidly disappearing while HDTV is gaining in popularity.

    hgmjr
     
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