Piston 2 has two channels, a and b, that lead to the two ends of the piston. If jet valve nozzle 1 is in its middle position, the fluid pressure is the same at both ends of the piston and it remains stationary. If jet valve nozzle 1 is diverted from its middle position, equilibrium is disturbed and piston 2 moves in the direction the jet valve nozzle is inclined. At this, four-way directional valve 3 admits fluid to one or the other end of servomotor 4.
$3751$SHP,Dr$