Active / Passive Locators
Active locators have some sort of signal generation device, in addition to a listening device. The two devices do not have to be located together.
Read more about this topic: Acoustic Location
Famous quotes containing the words active and/or passive:
“I am grown old and my memory is not as active as it used to be. When I was younger I could remember anything, whether it had happened or not; but my faculties are decaying now, and soon I shall be so I cannot remember any but the things that never happened. It is sad to go to pieces like this, but we all have to do it.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“The best emotions to write out of are anger and fear or dread.... The least energizing emotion to write out of is admiration. It is very difficult to write out of because the basic feeling that goes with admiration is a passive contemplative mood.”
—Susan Sontag (b. 1933)