Abstract: An automatic equalizer is described including a first transistor to the input of which a cable is coupled and which is branched in common emitter configuration and a second transistor branched in common collector configuration a collector of the first transistor being coupled to the base of the second transistor and the emitters of the transistors being intercoupled through a positive feedback circuit. In variation by small variation of a variable which is substantially independent from active parameters of the transistors results in a gain variation which is independent of the cable length in the lower frequency region and utilizes no coils.