Active Denial Technology uses radio frequency millimeter waves at a frequency of 95 gigahertz. Traveling at the speed of light, the millimeter wave directed energy engages the subject, penetrating the skin to a depth of only about 1/64th of an inch, or the equivalent of three sheets of paper. The beam produces an intolerable heating sensation, compelling the targeted individual to instinctively move. The sensation immediately ceases when the individual moves out of the beam or when the operator turns off the beam. There is minimal risk of injury due to the shallow energy penetration into the skin at this short wavelength and normal human instinctive reactions.
Videos of the Active Denial System:
From 2002 to 2007, the Active Denial System Advanced Concept Technology Demonstration integrated and packaged a large-scale version of Active Denial Technology into two system configurations. System 1, the technology prototype, integrated the technology into a High Mobility Multi-Purpose Wheeled Vehicle.
System 1 was successfully used in a series of land and maritime-based military utility assessments. System 2, a containerized version transportable via a tactical truck, successfully completed a capabilities and limitations assessment.
Both prototypes are long range, large spot sizes systems and are available for Service or Combatant Command exercises. System 2 is also suitable for operational employment.
You can see more images here:
Active Denial System Image Album on HMMWV In Scale
You can see a scratchbuilt ADS at this link: Scratchbuilt ADS System
There is an 18 page .pdf on the ADS here:
Articles on Active Denial System:
Global Security.Org article on V-MADS
Wikipedia Active Denial System Article
Defense Update Active Denial System Article