232 the control valve 400 may either be a fast or slow acting mechanical electromechanical electromagnetic pneumatic or hydraulic valve that controls the communication of the accumulator chamber 315 with the vent passage 226 the check valve 410 portion of the control valve 400 can also supply low pressure oil to the system 10 with continued reference to fig1 the control valve 400 is in an u201c off u201d position the off position is defined as that in which the solenoid valve 234 does not have power supplied to it and the control valve body 410 is at the resting position when in the off position the control valve 400 permits hydraulic communication between the accumulator chamber 315 and the vent passage 226 by way of the passage 222 the off position of the control valve 400 is used to provide positive power engine valve operation i e no compression release braking during positive power operation the system 10 is charged with low pressure oil from the passage 214 the check valve 216 prevents the oil provided to the master piston bore 210 and the slave piston bore 220 from flowing back towards the low pressure supply and thus provides automatic lash take up the oil provided from the passage 214 is not sufficiently pressurized to depress the accumulator spring 330 thus the accumulator piston 320 remains biased against the upper shoulder 314 when the master piston 120 is at base circle as shown as the cam 110 rotates the master piston 120 is displaced upward by a secondary lobe 114 the displacement of the master piston 120 causes the accumulator piston 320 to be correspondingly displaced downward against the bias of.