Multimedia Engineering
  Chief Leschi Video

    Baseband Multimedia Retrieval NTSC

    over Category 5

  • Source Interface: The source interface is located in the Headend and provides a means for the system to control various sources from different manufacturers employing different command encoding. Generally speaking, the source interface converts the system commands, in the form of Dual Tone Multi Frequency signals (DTMF) to manufacturers infra red control command language.


  • Multiplexer: The video and audio of every source in the system must feed a multiplexer. The multiplexer, sometimes called a modulator, mixes the video and audio channels together. This forms an analog composite baseband signal employing frequency domain multiplexing. Following the specifications set forth by the National Television Standards Committee (NTSC), the video signal consists of luminance information describing the amount of light in each point of the picture and a chrominance signal modulated on a 3.58 MHz. subcarrier which provides information about the hue (which color) and saturation (how much color). Left and right audio channels are modulated on subcarriers of 10.7 and 11.5 MHz. respectively, completing the composite. This signal is then fed to the switcher.