Principal axis connected with knob is available in shell, whose upper and lower section is respectively configured with synchronous upper and lower concave wheel and shifting fork.
在外壳内，设与旋钮相连 的主轴，其上下段分别装同步的上、下凹轮和上、下拨叉；
2
The hand knob and the shell employ a screwed joint, which can reach the self-hold request of the device.