Spool Valve Operation

spool valve
"A radially symmetrical valve, usually actuated by low pressure gas controlled through a pilot valve. In many spool valve based paintgun designs, the spool, or core of the valve, also functions as the bolt."

operation
the state of being in effect or being operative; "that rule is no longer in operation"
(computer science) data processing in which the result is completely specified by a rule (especially the processing that results from a single instruction); "it can perform millions of operations per second"
The fact or condition of functioning or being active
An active process; a discharge of a function
A business organization; a company
a business especially one run on a large scale; "a large-scale farming operation"; "a multinational operation"; "they paid taxes on every stage of the operation"; "they had to consolidate their operations"