I dont have access to my books so this is taken from memory,
the book is *The body Electric*-Robert Becker.
Robert Becker was an MD in a veterans hospital in the US,
approx from 1950-1980.
During this period he did a lot of research into the bodys regenerating abilities,
especially bone fractures and how there are systems of electric current going throughout your body
that are crucial to recovery.
These systems are important communication ways for the brain to coordinate what happens,
when and where in your body.
When working on salamanders he discovered that by cancelling out currents going over its head,
he could put it to sleep.
By use of magnetism or electrical currents he was able to induce Delta waves,
and monitoring the process he saw the salamanders wake up again shortly after the electric stimulation was stopped.
Relevance:
Well,Robert Becker was an outsider on low budget,yet he was still able to do this 50-60 years ago.
At the end of his career he did do some work for the government.
Anybody who is familiar with electromagnetic stuff affecting your body from the other side of a wall,
might see that to instantly put somebody out or keep them from waking up
would be a relatively short step further from his research.
If somebody were to use this kind of tech on you-in a hotel room,or even in your home
-it would leave no trace,if not deliberately.