Accordingly, as pointed out in Section 1.4, the problem of the identification of a lumped time-invariant system by black-box analysis amounts to a solution of the set of linear algebraic equations

−y = X h (4.1) where h is the vector of unknown ordinates of the pulse response, −y is the vector of the known ordinates of the output and X is the matrix formed as follows from the vector of the known input ordinates.