Abstract: In a serial binary digit stream, when a single bit follows at least two bits of the opposite polarity and is succeeded also by a bit of that opposite polarity, a comparator produces a correction signal which is combined with the first-mentioned bit so as to broaden it in time span. As a result, the amplitude of reception or reproduction of the broadened bit is enhanced so as to compensate for deficiency of amplitude which would result from the imperfection of the transmission channel or recording and reproduction process. The broadening of the critical bit pulse can be performed by a correction pulse that enhances its amplitude, followed by Nyquist filtering and then by amplitude limiting to the normal binary digit amplitude level, or else the broadening can be accomplished by providing a correction pulse shifted in phase by an adjustably shifted clock pulse or train.