accomplished by way of the following solenoid 920 preferably of the pulse width modulation pwm type pushes the spool valve 14 toward right such that the left portion 919 of the spool valve 14 still stops fluid flow at the advance end 98 but simultaneously the right portion 920 moved further right leaving retard portion 910 in fluid communication with duct 99 because of the inherent torque reversals in camshaft drained fluid from the retard chamber 93 feeds the same into advance chamber 92 via one way valve 96 and duct 94 similarly for the second scenario which is the retard scenario wherein a retard chamber 93 needs to be filled with more fluid than in the null position in other words the size or volume of chamber 93 is increased the retard scenario is accomplished by way of the following solenoid 920 preferably of the pulse width modulation pwm type reduces its engaging force with the spool valve 14 such that an elastic member 921 forces spool 14 to move left the right portion 920 of the spool valve 14 stops fluid flow at the retard end 910 but simultaneously the left portion 919 moves further left leaving advance portion 98 in fluid communication with duct 99 because of the inherent torque reversals in camshaft drained fluid from the advance chamber 92 feeds the same into retard chamber 93 via one way valve 97 and duct 95 as can be appreciated with the cta cam phaser the inherent cam torque energy is used as the motive force to re circulate oil between the chambers 92 93 in.