PURPOSE: To provide a increased sampling ratio without being accompanied with an increased on/off speed.

CONSTITUTION: Both edges of a PWM pulse are modulated. Next, sampling is operated at the double speed of a pulse turn-on speed, and the response time of a system can be reduced without increasing the operating frequency of a related controller. The special application of this system can be found in a continuously variable speed change gear system using a PWM control electric hydraulic valve for speed change rate control, line pressure control, and clutch control. A system for executing the PWM signal is provided with a duty cycle calculating device 120 connected to a timing circuit 128 for controlling input data reading action, circuit operation, leading and trailing edge modulators 135 and 138, and output pulse generator 130.