A system equalizer and a method of equalization employed in a repeatered submarine cable system, in which automatic gain controlled (AGC) submerged repeaters are employed to compensate for fluctuations of the cable loss caused by the temperature fluctuations in the surrounding environment of the repeatered submarine cable system. In a terminal equipment connected to the repeatered submarine cable system, the seasonal misalignment of the repeatered cable system is equalized by a switchable equalizer having a loss-frequency characteristic corresponding to the total of compensation errors in the AGC submerged repeaters. Short-term level fluctuations of the repeatered cable system are compensated by an automatic equalizer, which has a loss-frequency characteristic proportional to the square root of frequency f and is controlled by the level of a pilot signal transmitted through the repeatered submarine cable system. An unknown fixed deviation is finally equalized by a second adjustable equalizer.