PURPOSE: To automatically apply proper deterioration of a signal even to a coaxial cable with a different length by controlling a gain adjusting section and an amplitude slope adjusting section depending on the level of an input signal to be detected so as to compensate the loss of the input signal and the amplitude slope due to the cable.

CONSTITUTION: A gain adjustment section 1 amplifies a signal inputted from a terminal IN through a coaxial cable, an amplitude slope adjusting section 2 corrects the amplitude slope of a signal subjected to gain adjustment and part of the signal of the amplitude slope adjusting section 2 is outputted from an OUT terminal and the other part is outputted to an input level detection section 3, which detects the level of the signal sent from the amplitude slope adjusting section 2 and outputs 1st and 2nd control voltage corresponding to the level to the gain adjustment section 1 and the amplitude slope adjusting section 2 respectively. Thus, proper equalization is applied automatically even when the length of the coaxial cable differs and the complicated circuit is avoided.