Listen to the first use of forging die derived tissue density, and there is no sand hole, voice communication clearer.

Hose and listened to the first screw connections using packet hoop connected, voice prevent leakage

Fanning used to listen to the first high-pitched noises auscultation.

Equipped with a bell-shaped listen first used in the bass auscultation of the high noise.

Staffing table-style stethoscope auscultation skills commonly used in the pulse noise.