piston to control the flow of pumped fluid to a first working trailer braking circuit through an outlet and to a tank or reservoir through an outlet a flow control valve which provides a passageway communicating with a first flow path for pumped fluid to the spool valve and which is operable in response to pumped fluid pressure to control the flow of pumped fluid to a second working implement circuit through an outlet and a second flow path for pumped fluid extending between the inlet and spool valve independent from and parallel with the first flow path so that the spool valve controls the flow of pumped fluid through the second flow path to the fluid outlet leading to the trailer braking circuit application_number US 71844485 A description referring to fig1 this illustrates a control valve which is particularly adapted to control the operation of the brakes on the trailer unit of an agricultural tractor and trailer combination by distributing hydrodynamic fluid provided from a pump on the vehicle between the trailer brake circuit an implements circuit and a reservoir such distribution being effected in response to pressure derived from the hydrostatic braking circuit of the tractor unit the control valve comprises a housing 1 in which a pair of parallel bores 2 and 3 are formed the bore 2 containing a spool valve 4 and the bore 3 containing a flow valve 5 and a one way valve 6 respectively at.