Re: NZ phone line impedance

Discussion in 'NZ Computing' started by Mutley, Jul 18, 2003.

  1. Mutley

    Mutley Guest

    Master Tech © <> wrote:

    >On 17 Jul 2003 13:31:26 GMT, (Peter Gutmann) wrote:
    >
    >>
    >>
    >>For some unknown reason some people I know want to bring some flashy Phones
    >>with Everything over here from Germany to use (I guess the built-in foot
    >>massager and coffee maker is something they can't do without). Apparently
    >>European lines are 270 ohm + 750 ohm/150nF complex impedance, from memory NZ
    >>has straight 600 ohm lines. Does anyone know of any potential issues with
    >>this?
    >>
    >>(Before someone posts the obvious answer, I doubt anything less than "They
    >>will explode if plugged into NZ phone lines" will dissuade them).
    >>
    >>Peter.

    >
    >
    >
    >NZ phones are not 600ohms...
    >

    True. But on some old cable they work better when set to 600 ohms
    rather than complex impedance..
     
    Mutley, Jul 18, 2003
    #1
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  2. Mutley

    Brian Dooley Guest

    On Fri, 18 Jul 2003 13:46:55 +1200, Mutley
    <> wrote:

    >Master Tech © <> wrote:
    >
    >>On 17 Jul 2003 13:31:26 GMT, (Peter Gutmann) wrote:
    >>
    >>>For some unknown reason some people I know want to bring some flashy Phones
    >>>with Everything over here from Germany to use (I guess the built-in foot
    >>>massager and coffee maker is something they can't do without). Apparently
    >>>European lines are 270 ohm + 750 ohm/150nF complex impedance, from memory NZ
    >>>has straight 600 ohm lines. Does anyone know of any potential issues with
    >>>this?
    >>>
    >>>(Before someone posts the obvious answer, I doubt anything less than "They
    >>>will explode if plugged into NZ phone lines" will dissuade them).


    >>NZ phones are not 600ohms...
    >>

    >True. But on some old cable they work better when set to 600 ohms
    >rather than complex impedance..


    The belief in 600 ohms always was an act of faith, and it was
    more applicable to long physical lines, typically before the use
    of carrier circuits. Even then whether line impedance was 600
    ohm, or 400 ohms or 150 ohm was often enough a wild compromise.

    If you're driving a long physical line you really need to match
    impedances as best you can because maximum transfer of energy is
    necessary, but if it was ever achieved in practice it was by
    accident.

    In an urban environment you don't get this situation much any
    more.

    --
    Brian Dooley

    Wellington New Zealand
     
    Brian Dooley, Jul 19, 2003
    #2
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