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Silly question about 'Termination'

Discussion in 'Projectors, Screens & Video Processors' started by flibble, May 18, 2005.

  1. flibble

    flibble
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    I've gotten myself confused about the switch for signal termination on my projector Barco 800 Data (and also on my interface box).

    Basically is it correct that you need to turn the switch to on if *you do not have* anything plugged into the passthrough ? Or is it if you do have something plugged in.
     
  2. cosaw

    cosaw
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    Its a good question and one which I too would like clarifying - the manual seems confusing with regard to this aspect.
     
  3. Boy Lex

    Boy Lex
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    short answer... yes! On passthrough systems, 'on' is termination, 'off' is passthrough. It's necessary when you have a whole load of machines that are using the same signal. Working at a tv production company, we have a load of pro decks that each require a reference signal (just a black screen that acts as a common sync). Each of the machines is daisy chained together and if the last one isn't terminated, the signal is lost or if one is terminated early in the chain, the rest lose the signal. As far as I'm aware, if you are not daisy chaining to another machine/projector/tv, it shouldn't really matter where it is switched, and you'll get a picture either way.
     
  4. Barcoing Mad

    Barcoing Mad
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    Your coax cable is a 75 Ohm transmission line. When it comes to a stop, it needs 75 Ohms across it to prevent the signal being reflected. A single machine needs the termination impedance switched in.

    Daisy chained machines are connected across the line, preferably presenting it with very high impedances in parallel with the rest of the line. So the 75 Ohms is switched out for those machines, except for the last one in the chain that terminates the run.
     

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