Kurt Feltenberger wrote:
 > ... it's a sort of super EMP/radio wave device
 > that only effects the human neruo-muscular [system]
 > while leaving the brain undamaged and intact.
 > In short, the victim has no control over his
 > voluntary muscles but can breath and otherwise function.
<snip>
 > My question to the list is thus:
 > How possible are they in reality?

Impossible, given the quoted requirements above.

The central nervous system is covered in electrical insulators: skin,
muscle, bone and other tissues.

A taser works by the darts overcoming the impedance and getting enough
current to the muscles to produce fasciculations or involuntary
contractions, predominantly via surface spread of the current.

Transcranial magnetic stimulation relies on coils in contact with the
head that generate high intensity magnetic fields (2-3 Tesla, so tens of
thousands of times stronger than Earth's field).

They only allow the induction of currents 5-6cm deep, so don't reach
some important central bits of the corticospinal or rubrospinal tracts
involved in voluntary movement - but the motor strips of the cerebral
cortex and part of the internal capsules would be in range.

Magnetic resonance machines used in imaging can get above 5 Tesla in the
imaging volume. Visual illusions can be elicited by the time varying
fields, but nothing like the peripheral motor paralysis required in the
original post has been observed with the use of these high field
strength scanners.

As an aside, it is possible to induce malignant heart rhythms in these
machines by folding your arms across your chest so that a loop current
can be induced by the circulating blood...

So a ranged weapon like the anti-drone directional radio jammers or a
brain 'EMP' bomb is grossly impractical. The energy requirements get
very large thanks to inverse square or inverse with distance effects.

The taser is about as good as distant electrical stimulation gets -
which isn't very good. The Area Denial System which relies on
essentially microwaving the victim until skin pain receptors are
activated is another 'less than lethal electromagnetic weapon'.

Pragmatically, drug darts or chemical aerosols would be a better
investment of time and energy.

What would be plausible is a 'control helmet' as a near-future restraint
device. It would use transcranial coils to jam the motor cortices of the
cerebrum, preventing the initiation of voluntary movement. Potential
side effects would include seizures, strokes and death.

It would also be possible to induce involuntary movements - a 'puppeteer
device', so to speak - if the cortices could be mapped to sufficient
resolution ("What happens if I poke this bit of brain?")

Robert O'Connor