Desmodromic valve
internal combustion engines. The valves in question are the ones that allow air into the cylinder and (usually different ones) that allow exhaust gases out. This refers, for example, to the valve control system used in Ducati engines: both valve movements (opening and closing) are "operated". It is usual to say that action on the valve is "positive" in both cases, in other words, both strokes are "controlled".
In general mechanical terms, the word desmodromic is used to refer to mechanisms that have different controls for their actuation in different directions. It is derived from two Greek roots, desmos (controlled, linked) and dromos (course, track).
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