The symbols above are all of a directional control cartridge poppet valve. The top left image has a 1:1 ratio. This is indicated by the straight nature of the spool/poppet body.

Hydraulic symbols provide a clear representation of each hydraulic component functions. Many hydraulic symbol designs are based industry standards such as DIN24300, ISO1219-1 or -2, ANSI Y32.10 or ...