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:
“All is changed. All looks strange to me and gives me a feeling which I would rather get away from, although I know it to be the carrying out of natural laws. And I am not complaining. I am doing the same as many old people have done, I suppose, who have led an active life and suddenly find themselves living without a purpose. Oh, my heart is so full. I could write a big book on the subject of going out of this world gracefully.”
—Maria D. Brown (1827–1927)
“...if you are to gain any great amount of good from the world, you must attain a passive condition of mind. ...it is never to be forgotten that it is the rest of the world and not you that holds the great share of the world’s wealth, and that you must allow yourself to be acted upon by the world, if you would become a sharer in the gain of all the ages to your own infinite advantage.”
—Anna C. Brackett (1836–1911)