The relationship given in (2.24c) is called the “uncertainty principle” by analogy to the uncertainty principle of quantum mechanics. The latter states that the position and velocity of atomic particles cannot be simultaneously measured to any arbitrary degree of accuracy desired. Precise determination of one parameter can be had only at the expense of the other. Equation (2.42c) implied a similar concept, namely that both the time duration and the bandwidth of a signal cannot be made arbitrarily small simultaneously.