The paper shows that to improve the cable product quality and reliability, it is necessary to control and diagnose both current-carrying conductors and insulation at all stages of their life cycle. However, common methods and devices make it possible to control only one specific parameter. To ensure the simultaneous control of these parameters, a new method has been developed for complex non-destructive testing of cable products. What makes this method unique is the fact that resonance properties of a low-frequency conductometric capacitive cell are used and this cell contains an electric choke as an additional element and two cylindrical electrodes with a cable placed inside. The choke connected in series with one of the electrodes forms a series oscillating circuit in the conductometric cell operating in the quasi-resonant mode, whereby its output information signal reaches its maximum possible value. Moreover, it is proved that the signal real component is a function of the active resistance in the metallic cable core controlled section, and its imaginary component is a function of the volumetric electrical resistance in the cable insulation. The developed method and its proposed hardware implementation variant make it possible to carry out control and diagnostics of cable products both during their manufacturing and in operating conditions without their integrity violation.