Abstract: A module for receiving a plurality of signals that are modulated with a common carrier, where each of the signals includes information that enables a determination of a distance from said receiver to a source that transmits the signal, and outputs to outside the module a digital representation of a downshifted replica of the received signals or, alternatively, outputs a stored and delayed version of the downshifted replica of the received signals together with information about the delay.

Abstract: A receiver that receives a plurality of signals that are modulated with a common carrier, where each signal of said signals originates at a different source and experiences a transit delay and Doppler frequency shift before reaching the receiver, and where the transit delay and Doppler frequency shift are related to position and movement of each of the respective sources. The receiver includes means, such as a directional antenna, to ensure that the received signals are bona fide, or at least not subject to the same bogus signal or signals to which a second receiver may be subjected.