PURPOSE: To make it possible to reduce costs to a large extent, by performing the operation and execution of exciting time for solenoid controlled valves with respect to the preset pressure for a direct pipe automatically based on the preprogrammed procedure.

CONSTITUTION: A computer 22 is connected to solenoid controlled valves 26a and 26b on the side of a vehicle 21. The computer 22 is connected to a direct pipe 25 on the side of the vehicle 21, which is controlled by the pressure of the solenoid controlled valve 26a and 26b through a P/E converter 23. Then, exciting time T for the solenoid controlled valves 26a and 26b is controlled, and the pressure for the direct pipe 25 is set. At this time, a desired preset value and the first sampling time data are inputted to the pressure setting program of the computer 22. Then the pressure change characteristics of the vehicle 21 are judged. Thereafter, the operation and execution of the exciting time T for the solenoid controlled valves 26a and 26b with respect to the preset pressure of the direct pipe 25 are automatically performed based on the preprogrammed procedure.