1. There are several control types: plunger, roller plunger, roller lever and one way roller lever, 2-Pos. 3-Port and 2-Pos. 5-Port.
2. Mechanical valves usually use the externa forces from cams or rams to change the fluid flowing directions.
3. When the external forces disappear the valves reset automatically.
4. The P port and R port of a 2-Pos. 3-Port valve can be exchanged so as to change the valve from normally closed to normally open.