within the cup 22 are two electromagnetic coils 80 and 82 the coils 80 and 82 are separated by an annular ferrous spacer ring 84 the coils 80 and 82 are like the coils described in u s pat no 5 069 420 referred to above although two coils are provided in the preferred embodiment disclosed herein briefly energizing either coil with a variable direct current produces a magnetic field the strength of which varies with the amperage of the current energizing coil 80 produces a magnetic field which draws the armature 66 leftwardly as viewed in fig1 thereby diminishing the size of spring cavity 73 and increasing the size of spring cavity 63 this movement compresses spring 74 and allows spring 64 to extend thereby reducing the spring force biasing spool 42 into the sealing position energizing coil 82 rather than coil 80 produces a magnetic field which draws armature 66 to the right as viewed in fig1 thereby diminishing the size of spring cavity 63 and increasing the size of spring cavity 73 this movement compresses spring 64 and allows spring 74 to extend thereby increasing the spring force biasing spool 42 into the sealing position therefore energizing coil 80 reduces the force exerted by spring 64 on metering spool 42 so that a lower pressure in port 12 will cause metering spool 42 to open to a given open position conversely energizing coil 82 will compress spring 64 thereby exerting a larger force tending to hold the metering spool 42 closed so that a.