The reconstruction of trigonometric polynomials, a specific class of band limited signals, such as ac signals, from a number of integrated values of input signals is in the focus of this chapter of our monograph. It is widely applied in signal reconstruction, spectral estimation, system identification, as well as in other important signal processing problems. We are proposing a practical and new algorithm for signal reconstruction and discussing potential applications to recover band-limited signals in the form of Fourier series (with known frequency spectrum but unknown amplitudes and phases) from irregularly spaced sets of integrated values of processed signals. Based on the value of the integer of the original input (analogue) signal, a reconstruction of its basic parameters is performed by the means of derived analytical and summarized expressions. In this way, we create a possibility to conduct a subsequent calculation of all the relevant indicators related to the monitoring and processing of ac voltage and current signals. Computer simulation demonstrating the accuracy of these algorithms and potential hardware realization is also presented. The chapter investigates the errors related to the signal reconstruction, and provides an error bound around the reconstructed time domain waveform.