NOVELTY - The first and second adsorbent modules are configured for transferring the first product gas between the adsorbent modules over multiple discrete pressure levels to maintain uniformity of gas flow.    USE - For separating gas fractions from a gas mixture.    ADVANTAGE - Achieves uniform gas flow between each stage. The system is suitable for high volume and high frequency production, which reduces the energy losses associated with prior art devices, and can be readily configured to obtain the desired process results.    DETAILED DESCRIPTION - The system comprises    (a) a first adsorbent module including a first gas inlet for receiving a gas mixture, at least one bed of first adsorbent material in communication with the first gas inlet for adsorbing a gas mixture component from a gas mixture, and a first gas outlet in communication with at least one first adsorbent bed for receiving a first product gas excluding the adsorbed gas mixture component, and    (b) a second adsorbent module including a second gas inlet coupled to the first gas outlet for receiving the first product gas, at least one second bed of adsorbent material in communication with the second gas inlet for adsorbing a first product gas component from the first product gas, and a second gas outlet in communication with the at least one second adsorbent bed for receiving a second product gas, the second product gas excluding the adsorbed first product gas component.    The first and second adsorbent modules are configured for transferring the first product gas between the adsorbent modules over multiple discrete pressure levels to maintain uniformity of gas flow.    An INDEPENDENT CLAIM is included for a method of separating components of a gaseous mixture using the gas separation system.    DESCRIPTION OF DRAWING(S) - The drawing shows a two stage rotary PSA module.    Two stage apparatus (300)    Rotary PSA modules (301',302')    Connecting compartments (304',305')    Throttle orifices (350',360')