... actuators.Basically these valves consist of housing (1), poppet (2), compression spring (3), control spool (4) as well ... to B, in the counter direction the poppet (2) is held on its seat by the system pressure ... control pressure is necessary.Type SV ... A ... and SL... A ... (with pre-opening)This valve has a ... poppet (5.1) leaves first then the poppet (2) leaves from the seat. Now the valve may also ...