PURPOSE: To realize data communication by a high baud rate without using the element of a high speed response in data communication by a digital signal.

CONSTITUTION: Data (b) is outputted from a memory part 2 by an instruction from a control part 1. The data (b) is set in one of two shift registers 7. A reference clock is inputted to the shift register where data (b) is not set, and serial data is outputted. The arbitrary pulse string is outputted at high speed without using the element of the high speed response by permitting the two shift registers to alternately set and output data.