Sean Breheny wrote:

> Well, I think what he was saying is that no current would flow thru
> the skin UNTIL the tissue became damp, at which point the alarm would
> go off anyway,and we could turn off the current and keep the alarm
> going until someone arrived to help the person.

  An interesting point of the "old" relay logic - the "locking" contact
in parallel with the sensor does in general remove the voltage from the
sensor.  Remember the "sequence" doorbells, mains operated with the
light wired across the push?  On simple doorbells, the light goes out
when the button is pressed, but on those, the light went out until the
sequence was finished.

  This is in general *not* the case with an R-S logic latch, but can
most certainly be arranged to be so.

> This way,there would only be a fraction of a second exposure to the
> current, and ONLY when the problem actually occured.

  I can't see that the current is a problem overall.  I *do* assume that
the electrodes are isolated by (polyester, not electrolytic) capacitors
and the monitoring voltage of a couple of volts is constrained to
intermittent pulses at a very low duty cycle.

  Contrary to a previous proposition, ions do *not* take significant
time to accelerate; the conductivity is evident in microsecond pulses.
The principal reason not to use too high a measurement frequency is that
you will spuriously detect the capacitive reactance of your electrodes
and for that matter, body membranes.
--
  Cheers,
        Paul B.