PURPOSE: To improve the quality of a reproduced picture by wave-form-shaping binary signals at both transmission and reception sides having reverse relation to the variation of the input-output pulse mesial magnitude of a thin line produced by transmission characteristics on the system which transmits binary signals after ternary-converting the waveform.

CONSTITUTION: Signal A is written into shift register 23 from terminal 21 by sampling clock 22. The black-signal length of the input signal is counted by black-signal counter 24, and the white-signal length by white-signal counter 25. Both counting contents are stored in memory circuits 28 and 31 respectively. By analyzing the relation between the black-signal length of memory circuit 28 and the white-signal length immediately before the black signal from memory circuit 31, analyzer circuit 32 allows a signal indicating the left edge of the black part of the screen to pass through as it is when the white-signal length is not long enough, and transmits a signal expanding the white-signal part before the rise of the black signal into black to register 23 when the white-signal length is more than 18-sampling.