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:
“True contentment is a thing as active as agriculture. It is the power of getting out of any situation all that there is in it. It is arduous and it is rare.”
—Gilbert Keith Chesterton (1874–1936)
“She has taken her passive pigeon poor,
She has buried him down and down.
He never shall sally to Sally
Nor soil any roofs of the town.”
—Gwendolyn Brooks (b. 1917)