
A manual selector valve lets one set of hydraulic services feed several different functions, one at a time. Turn the lever to select which outlet pair is live; the rest are isolated.
On a tractor or a truck this is what turns a single pair of remotes into three. No electrics, no solenoids, nothing to fail — just a spool and a detent.
| Type | Behaviour | Use it when |
| Open centre (GCA) | Unselected ports are connected to each other, so trapped oil can escape | Cylinders may be moved by external force, or thermal expansion could build pressure in an idle line |
| Closed centre (GCC) | Unselected ports are fully blocked | The unselected function must hold its position — the usual choice for a load holding circuit |
If in doubt, closed centre. It is the safer default for anything holding a load. Choose open centre deliberately, when you know trapped pressure is the bigger risk.
Manufactured by CBF Hydraulic, Montecchio Maggiore, Italy. Cast iron body, manual lever, 350 bar rated.