Results of electrical measurements performed on diphytanoyl phosphatidylcholine planar membranes are presented. The membranes are held in current-clamp conditions and a transition to a low-resistance non-stationary flicker-fluctuating state is induced. In these conditions, the membrane is stimulated by a sine-wave input current and its electrical behaviour is completely characterized in a frequency range between 0.1 and 10 Hz. In this range, the sine-wave membrane response turns out to be linear.