PURPOSE: To improve a scramble effect and to cut down costs by sampling a transmission signal and its inversion signal with the aid of a clock signal subjected to pattern setting and its inversion signal, scrambling them through addition and descrambling them with the aid of a clock reproduction signal under the same constitution.

CONSTITUTION: For outputting a prescribed clock pulse, the transmission signal A inputted to an input terminal 1 becomes a waveform B when it passes through the 1st switch means 3 and goes to a waveform C when it passes through the 2nd switching means 5. As a result, an output signal from an adder 7 becomes a waveform D, is completely deformed, and demonstrates a scramble effect. Since a clock pattern generator 9 sets the clock signal A to a sample pulse by a pattern having a frequency with different iterations, the scramble effect is further improved. A reception side operates in the reverse way of the above- mentioned procedure, and descramble is completed. A normal signal is outputted to an output terminal 8.