Measurements of the frequency and temperature dependence of the noise spectrum and of its frequency exponent have been performed on thick-film resistors and, together with the direct plots versus the frequency logarithm of the spectrum-frequency product, they are used to check the island model of the flicker noise. It is shown that the wide dispersion of the island relaxation times, necessary to originate the flicker noise, is due to tunnel emission and/or thermal activation processes of electrons from localized states, and to the exponential dependence of their emission probability on random variable distances and activation energies, whose distribution functions, means, and variances are determined both theoretically and experimentally. I. PREMISE The island model of the low-frequency excess noises' shows that these phenomena, including the flicker noise, are generated by localized states, called islands, that exchange charge carriers with the surrounding conductive medium through tunnel emission and/or thermal activation processes. This latter type of process leads to a strong temperature dependence of the conductance 6 of the islands and of their relaxation times r Further. more, the model predicts that the product fSy(f, T) between the frequency f and the power spectral density Sq of the voltage fluctuations is related to the distribution function D of the logarithm of 6, calculated at — ln(f /f„), by the relationship fSv(f, T)= ((b V)~ ),D( — ln(f/f„) ), where ((AV) ), is the variance of the voltage fluctuations, f„ is a reference frequency, and T is the temperature. Consequently, a careful analysis of measured data of fSv vs ln(f/f„) over wide frequency and temperature ranges should be able to give interesting physical information of the investigated system and, together with a detailed model of the distribution function of the island conductance logarithm, should allow us to check quite easily the validity of the island theory of the flicker noise. In this paper we will show that both these goals have been attained by means of the study of the excess noise in thick-film resistors and of a measuring system that includes a digital signal analyzer that