In The Trenches
to the chassis. This was not too much
of a problem, as long as everything
was insulated — hence the plastic
case and plastic knobs. These knobs,
however, were just pushed onto the
split-knurled shafts of the controls.
They were always falling off and had
to be pushed back on. Often times,
they fell off and rolled under the
couch or just got lost. This meant
that the radio was often operated with
exposed metal that was in direct
electrical contact with the chassis.
Now, suppose you were bathing in
your cast iron tub with nice copper
pipes going deep into the ground. The
radio is playing your favorite song, so
you reach out of the tub with your wet
hand to turn up the volume. The knob
is gone, so you twist the bare metal
that connects to the chassis, which is
connected to the hot lead of the AC
power. What do you think happens?
Better circumstances for electrocution are difficult to achieve. The
current flows through the torso with
low resistance at every point directly
to an excellent ground. Even if you
aren't immediately killed, there's a
good chance that you will drown.
When the electricity passes through
your hand, it contracts onto the shaft
because of muscle spasms. Then,
when you fall, the radio is pulled into
the tub with you. (Deaths from this
scenario were not all that rare.)
There are two points to this. The
first is that the death was usually
attributed to the radio falling into the
water and that was what caused the
electrocution. However, if you stop
and think, you will realize that this is
unlikely to cause a significant shock.
Electric current wants to go to ground.
It takes the path of least resistance.
Assuming the radio doesn't fall into
your lap, the easiest path is either
through the water and metal tub to
ground or through the return wire of
the radio itself. Even if it does fall into
your lap, the current isn't likely to pass
through the torso and cause your
breathing or heart to stop. (Although I
haven't personally tried it.) The second
point requires some additional information. On the cord of all of these radios
was a label that said "UL Approved."
UL means Underwriter's Laboratory.
That sticker meant "safe." Most
everyone thought that the radio was
safe. The truth was that the UL mark
only referred to the power cord. The
power cord was safe when used properly. The radio was not UL approved.
I'm using this example to graphically illustrate many facets of safety
and risk: an unsafe design based on
cost-cutting measures; the perception
of safety with the UL sticker on the
cord; the ignorance of the user; the
tacit acceptance of major manufacturers and government. Of course,
such things could never happen today.
Or could they? I can think of several
examples that parallel the radio
NUTS & VOLTS
Circle #110 on the Reader Service Card.