Use the hearing to determine if the
hydraulic jack system is working properly, usually four listening: one listening to noise. That is, whether the healing hydraulic pump and system noise are too large, whether the components such as
hydraulic valves have a scream; two listening sounds. That is to listen to whether the impact is too large when listening to the implementation component; three listening to the sound, that is, there is no thin and continuous sound inside the oil circuit board; four listening to the sound, that is, whether there is a hit hit in the heroic press and pipeline Voice.