A directed RF transmitter ideally used to stop riots. The prototype model was designed to shoot out a 95GHz beam at an unspecified amount of power, causing near-immediate pain which would supposedly disperse a rioting crowd. The scheduled release of this weapon in Iraq is to be in 2006, so it remains to be seen whether it'll go through or not, what with all the political bullshit it's going through.
Now for the fun stuff. I've been working with Microwaves/RF for a good 4 years or so, and a lot of people are worried about the hazards to a rioting crowd caused by this weapon. I'll bore you, the reader, with a minimum of numbers; hopefully, the terms I do use will be easily understandable with a minimum of link-chasing for definitions.
First, the hazards to the eyes. Indeed, RF radiation (this will be shortened to RF for the remainder of the w/u) is a hazard to the eyes. Looking into a transmitting microwave dish may cause permanent eye damage. On the other hand, this weapon is designed to be swept across a crowd over a short period of time. Ideally, the exposure to rioters would be a second or two at most, unless someone was stupid enough to actually remain in the path of the beam. Is this enough to damage eyes? That's for the scientists and people who are good with numbers to figure out.
Second, the danger of skin burns. Exposed metal, jewelry, and anything else which conducts heat will heat up quite a bit more quickly than bare skin, and this could cause burns. On the other hand, this would aid in dispersion of the crowd, and while the burns may be painful, they will heal eventually. The time of exposure wouldn't (shouldn't) be enough to heat the metal up on the inside (where it contacts the skin) to the point where it would produce more than a few moments of burning.
Now for the fun part: Making your own! I won't give too many details, but the concept is deceptively simple. You'll need a six-foot dish or better, a klystron or other RF amplifier, a means to power the klystron (the fun part), something to generate a 95GHz RF signal at about half a watt, and waveguides to carry the amplified signal to the dish.
If you're making one of these at home, I doubt you're worried about the safety part of things, but I'll include it anyway. Don't try this at home, don't point this at your parents, kids, dog, cat, self, friends, enemies, or local, national, or international government agency.
Anyway. First, your power generation. A 30kW generator or better should work for this. You'll need something to change 120VAC or 208VAC three-phase into something amplifiable to a rough 8kV or better, depending on the klystron/RF amplifier you find. Unfortunately, having checked a few companies, there aren't any publically available klystrons that go above 30GHz (Ka-band), but I'm sure you can substitute that. A few more skin burns, no problems! You're probably not worried if you're making this anyway. Obviously, you'll need to find something to amplify the 8kV, which I'm sure a resourceful person could find.
Next, you need to find something to produce your base 95GHz or 30GHz frequency. I'll work with 30GHz from here on, since if you've followed me this far, you're not too worried about safety, and don't mind causing a few skin burns, death, destruction, whatever. Anyway, wires and solder are all that are needed at this point in the process. A frequency standard of some sort to generate 30GHz, and a little bit of power siphoned off from the main supply to your amplifier, and you're set.
Feed the signal from the frequency standard into the klystron using shielded wire. Coaxial cable stolen from your TV's cable line should work well enough for your purposes. Out of the klystron, you need a waveguide, led to your dish. Get a flexible one, so you can move the dish without moving what it's mounted on - the entire assembly will probably weigh about 300-500 pounds unless you're really creative. Once you've got all that, you're set. You've got your own (crappy AND dangerous) ADS!
I say again: Don't try this at home. It's not my fault if you burn your eyes out, Fallout 2 style.