can facilitate an optimized configuration of camshaft rotor 220 and brake rotor 240 to avoid leakage and friction between the two rotors as they move relative to one another in operation of the phaser further openings 282 284 may be fitted with check valve s and other apparatus not shown to further control the flow of oil between respective sub chambers 226 a 226 b and 228 a 228 b referring now to fig7 an exemplary brake 150 is shown for actuating a brake rotor 140 in a camshaft phaser 100 improved in accordance with the invention various brake mechanisms are envisioned within the scope of the invention for example mechanical friction brakes actuated with an electromagnetic actuator neither is shown or a known electromagnetic eddy current brake 160 a presently preferred type of brake is an electromagnetic hysteresis brake 162 such as is available from magtrol inc west seneca n y these types of brakes are commonly used as loads in dynamometers and have three advantages they are contact less producing torque through a magnetic air gap without the use of magnetic particles or friction components and hence little wear is to be expected they are easy to control since the amount of torque is a direct monotonous function of current which is generally linear until magnetic saturation and the torque they produce is generally independent of rotational speed the hysteresis effect in magnetism is applied to torque control by the use of two basic components a reticulated pole structure 164 and a specialty steel rotor shaft assembly 166 fastened together but not in physical contact with pole structure 164 pole structure 164 may be formed of any soft magnetic steel either.