t n for each sensor but since q values are not stored for q sensors we will continue ignoring the index q in the functions h q t n now by correlating all of the functions h t n with the received signal r u2032 n we can find which one produces the largest correlation peak and thus determine the sensor id and the atmp value at the sensor location typically the functions h t n are time reversed and conjugated to create a u201c matched filter u201d mf t n this conforms with the u201c black box u201d concept of linear systems theory where an input signal is convolved with the impulse response of the black box to produce an output signal which can then be cascaded on to the next black box this black box concept is also used by equation 5 to generate the actual echo signal and it is similar except that equation 6 uses notation appropriate to processing the received signal equation 6 results in a u201c cf u201d or correlation function since due to variable amplitude and variable initial delay r u2032 k is not exactly equivalent to mf n k so it is not an acf although the equations 5 and 6 look very similar the concept in the receiver processing is quite different from the concept of generating the echo signal from a real transmitted signal the generation of the echo signal equation 5 is a true black box cascadable input output operation in that it produces an output signal y n when given the transmitted signal s n as input and it doesn 39 t matter if h n and.