U.S. patent #6782847 granted August 31, 2004 to David Shemesh and Dan Forman, both based in Israel, for an ?automated surveillance monitor of non-humans in real time.? The patent contains a sequence of three drawings?reproduced here?that, by themselves, pretty much explain the inventors? thinking.
In this technical drawing, two of the sensor-bearing dogs are alarmed by a passing terrorist. Both dogs say ?WOOF WOOF WOOF.? Shemesh and Forman write that ?FIG. 1B illustrates a situation wherein the amplitude and perhaps also the frequency of the barking of a dog indicates an alarm situation.?
(That?s an excerpt from the article ?Plucked from Obscurity: Technology + Animals,? published in AIR 14:1.)