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Re: OT (most likely) strange modem disconnection when using USB drives



On Tue, 2007-10-02 at 12:47 -0500, Mikkel L. Ellertson wrote:
> If you can, check out the "polarity" of the outlets.
> I know this is usually used to refer to DC circuits, but you can run
> into problems if the phases on an AC circuit are reversed on one or
> more outlets.

One of the first things I checked, was to grab the multi-meter and check
voltages between each of the three pins.  'twas as I expected them to
be.

Australia:  We only have grounded outlets for general purpose outlets,
and special purpose outlets are a bit of a rarity.  Although we do have
two-pin plugs, for some equipment.  The GPO looks like:

Mains supply  /   \  Mains current return

                |    Protective earth (equipment chassis)

If they'd had any sense, they would have put the earth up at the top,
I've been giving a huge zap in a bank when a metal plate fell into the
top of an outlet.  They don't like hearing loud bangs and screams in
banks.

There's 240 Volts on the mains supply pin, the return and earth connect
together at the distribution box.  Plugs can only be inserted one way,
thanks to the angle of the blades.

We also have earth leakage protection breakers.  If there's a difference
in current between the supply and return line, such as some of it is,
instead, going through the earth, something else, or a person, the power
is cut off.  Well, so says the theory...  /me briefly brushes finger
past a mains wire, can definitely feel the voltage, and not a mild
tingle, circuit breaker didn't break the circuit.

Before someone says, "DON'T DO THAT!"  I have some twenty-odd years of
working in electronics, and the mains voltage is smoooooth compared to
getting a 24,000 Volt shock from the inside of equipment you're working
on.  You'd swear that you could count the cycles.  Getting a bite is
just an occupational hazard, you get used to ripping your hand away at
the slightest hint of pain.

It's a bit like trying to tell a motor car repairman that he cannot do
anything under the bonnet while the motor is running.  It's just not
practical.  ;-)  But I will say "DON'T DO THAT!" to anyone who's not
familar with working with electricity.

-- 
(This box runs FC5, my others run FC4 & FC6, in case that's
 important to the thread.)

Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.


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