What does it mean when there is an icon of a breathing valve with a capital M written inside a regular hexagon?
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As the title suggests, there is a breathing valve on the diagram provided by a foreigner, which consists of three triangles. The next one below, with two on top that are symmetrical left and right. The triangle on the left is connected to a short line; the triangle on the right is also connected to a short line, and the right end of that short line is connected to a regular hexagon, within which a capital letter M is marked. What does this M mean?
It won’t be shown in the image. Maybe I didn’t explain it clearly; no one came :@
Could the M of the valve refer to manual or automatic?