NEtworking question -- Somewhat off toipic

Discussion in 'Computer Security' started by John Hyde, Jan 23, 2005.

  1. John Hyde

    John Hyde Guest

    This question is not about security per-se, but has to do with
    networking hardware. Since this is the only group I moniter that is
    even close, I hope you will indulge me.

    Here's my situation:

    I am helping a friend configure a home network so that
    he can VPN his laptop to work. His tech folks setup the laptop and sent
    him homw w/ a box of stuff. Problem is the router came with a 240 volt
    input transformer. If it had been bought at office depot or some such,
    no problem, exchange today. But there is a vendor involved, and yadda,
    yadda, yadda . . . It will take several days and my friend would like
    this to happen asap (Mainly because of my availability)

    The transformer states that it delivers 12 VDC at 1.2 amp to run the
    router. The router can support four linked computers but my friend only
    needs two.

    I have a spare transformer that is rated 12vdc, 800 mA, correct
    polarity, correct connection etc.

    So here's the question: Does anyone know if, since the router does not
    have to support it's full capacity of connections, it will draw enough
    less current that I can use this transformer temporarily?? Probably a
    week at most. I don't really care about the transformer itself since it
    came from my "junk box", but I do care about (1) fire hazard and (2)
    frying the router.

    Thanks for any thoughts.

    John Hyde, Jan 23, 2005
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  2. John Hyde

    donnie Guest

    I don't think the the amout of connections determine the amps needed
    to work the router. At the same time, I don't think that you would
    blow anything trying your transformer.
    donnie, Jan 23, 2005
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  3. John Hyde

    Jim Watt Guest

    The number of computers connected is immaterial, the bulk of the
    current is drawn by the router without any connections.

    Try the 800ma suppy, the worst that can happen is that it gets too
    warm, after around an hour it will have achieved a steady state.
    if its too hot to touch (>50F> then its a bad idea to continue.

    Ensure that it is a DC supply and that the polarity is correct, modems
    tend to use AC supplies and some equipment has center negaitve rather
    than the normal center positive.

    You are not going to fry the router as you are feeding it what it
    wants and if its taking a nominal 12v it certainly contains its own
    voltage regulator(s).

    If you are anxious, meter the supply before using it, but although it
    says its 12v it may be as much as 16v without a load.

    Although its not strictly 'computer security' designing reliable
    systems requires a stable electricity supply, and a controlled
    environment where equipment does not overheat;. Physical
    security and a stable environment are as important as keeping
    out Mr hacker.
    Jim Watt, Jan 23, 2005
  4. John Hyde

    John Hyde Guest

    Thanks for your thoughts, and your's too donnie. I kept digging in junk
    boxes and found another adaptor that was also correct voltage and
    polarity AND would deliver up to 1.5 amp, so all is well. But, as
    always, I appreciate your perspectives to expand my knowledge a bit.


    John Hyde, Jan 24, 2005
  5. John Hyde

    IPGrunt Guest


    This must be some industrial strength router to have a 240v input.

    Today being Monday I'm sure you already plugged this in and are running,
    but you should know two things: 1)the router (or any electronic device)
    will only draw as much current (in mA) as it needs, and the current value
    stamped on the transformer is actually calculated from the power rating at
    which the transformer is designed to work (volts * amps = power in watts).
    Therefore, use your 1500ma transformer. The 800 ma transformer may overheat
    (and fry) when called on to provide 150% of its rated power (1200ma/800ma =

    -- ipgrunt
    IPGrunt, Jan 24, 2005
  6. John Hyde

    John Hyde Guest


    Not really. As mentioned, the specified output was 12v @1.2 A. I figure
    this one was packaged for use where there is 240 v in common use.
    Perhaps somewhere else in the world.

    Thanks for the input,

    John Hyde, Jan 25, 2005
  7. John Hyde

    Martin Guest

    the whole of europe
    Martin, Jan 25, 2005
  8. | John Hyde wrote:
    | >
    | > Not really. As mentioned, the specified output was 12v @1.2 A. I figure
    | > this one was packaged for use where there is 240 v in common use.
    | > Perhaps somewhere else in the world.
    | the whole of europe

    Close but no cigar. Europe actually uses between 220 and 240 volts (and at either 50 or 60Hz)

    As does a large chunk of the world apart from the US, some of S America,
    and a little bit of the Middle East a tiny part of Africa, Japan and some little island
    offz the coast of China.

    <> has the gory
    details. Although it appears to be incorrect for the UK, with is 240v rather than
    the stated 230v.

    No idea whether the voltage range and/or frequency range make a real difference to the device
    working or not. Hopefully an Electrical Engineer will be along to enlighten us.
    David Postill, Jan 25, 2005
  9. John Hyde

    Jim Watt Guest

    The UK and Australia are supposed to be 230v whereas Europe is
    nominally 220 volts. Its all 50Hz except for the US I think Japan,
    and nuclear submarines. However the quoted voltage varies
    depending on conditions within a tolerance, ours is nominally 240v but
    often at 250v

    Thats one reason for running computer stuff via a UPS - mine
    recorded a 270v surge recently. The newer switched mode
    power supplies are more forgiving and some are rated to run
    110 - 240v without any adjustment.

    If its a regulated power unit it makes little difference and in any
    event there will be voltage regulators inside the unit.

    The question whether the power supply can deliver adequate
    current to run the unit without overheating, and that it has the
    right polarity. In practice you can get away with a lower
    current supply. Just keep an eye on the temperature for the
    first hour or so.
    Jim Watt, Jan 26, 2005
  10. John Hyde

    IPGrunt Guest

    Larger servers have a 240V service input. So, some of the networking
    equipment designed for server racks also use 240V inputs. (So does my
    Kenmore electric oven, by the way.)

    That's why I thought this was a router designed for high-end server

    By the way, an OP mentioned polarity of a transformer. This is very
    important, but generally the connectors for + and - polarity sources are
    not compatible with eachother, but, and a big but, I've worked in
    production environments where a tech will solder the wrong type of
    connection for expediency so you do have to check if you work in this

    -- ipgrunt
    IPGrunt, Jan 26, 2005
  11. John Hyde

    Jim Watt Guest

    Not the transformer, as that does not have a polarity being an
    ac device, and often now the power supply brick does not actually
    contain a transformer.
    I have samples where it is +exactly+ the same, and the one that
    has melted as a result of plugging it into some equipment which
    was well protected.

    Its a known problem with ham radio where Yaesu use center
    negative yet the same connector as everyone else where the
    norm is center positive.

    Smoke happens.
    Jim Watt, Jan 26, 2005
  12. John Hyde

    IPGrunt Guest

    Jim Watt <_way> confessed in

    Amen, brother.

    -- ipgrunt
    IPGrunt, Jan 27, 2005
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