NOVELTY - An electrolyzer cell comprises cathode of tubular configuration within which is disposed anode separated from cathode by separation membrane of tubular configuration which divides electrolyte chamber into anode sub-chamber and cathode sub-chamber. Hydrogen gas generated within cells is removed through hydrogen gas take-off lines and hydrogen manifold line. By-product oxygen is removed from cells by oxygen gas take-off lines and oxygen manifold line.    USE - For electrolyzing water to generate pressurized hydrogen and oxygen (claimed) on site at locations such as service stations for hydrogen fuel cell-powered automobiles; service stations, hardware/home improvement stores, and local energy distributors for retail sale of hydrogen fuel through high pressure canisters; and in residences, factories, and office buildings for on-site energy storage and/or use in fuel cell or internal combustion engine based portable power supply or home, garden or other appliance applications.    ADVANTAGE - The high pressure hydrogen up to at least 10000 psig can be produced without the need of separate compression equipment. The coaxial anode/cathode configuration allows very high pressure hydrogen generation with practical wall thicknesses of conventional materials in the containment vessel provided by the cathode. The value of the apparatus is further enhanced by the use of advanced pressure-containment materials, such as composite structures, which may make practical larger individual cell sizes at elevated pressures. The coaxial configuration also allows optimization of the surface areas of anode and cathode. Independent gas/liquid separators are used for each of the hydrogen and oxygen production sides. This allows multiple gas generation cells to be connected to common gas/liquid separation vessels and the utilization of a liquid electrolyte level control system. A low-cost pressure seal design for entry of anode into gas generation cell enables satisfaction of high-pressure and electrical isolation requirements at reasonable cost. The apparatus provides simple inexpensive control strategy for untended operation during hydrogen production, including automated control of level of liquid electrolyte or control of the differential pressure between the separators and release of generated hydrogen and oxygen gases such as high-purity gas products. The ability of the apparatus to enable hydrogen and oxygen production at pressures of up to at least 10000 psig exceeds the highest direct generation pressure of 3000 psig as attained by prior art electrolyzers. The high pressure hydrogen production is performed in a unique way that reduces the component cost and system complexity so that the equipment is easily affordable by individuals for commuter vehicle home fueling and for small fleet fueling applications. The apparatus is scalable to any given production capacity and is also practical for service-station type applications for dispensing of hydrogen to fuel-cell-powered vehicles and equipment.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) an electrolyzer apparatus including:    (a) an array of individual electrolyzer cells;    (b) first gas-flow conduits connected in gas-flow communication between the respective cathode sub-chambers and a first gas collector; and    (c) second gas-flow conduits connected in gas-flow communication between the anode sub-chambers and a second gas collector    (2) a method of electrolyzing water to generate pressurized hydrogen and oxygen by utilizing the electrolyzer.    DESCRIPTION OF DRAWING(S) - The drawing shows the electrolyzer apparatus.    electrolyzer cells (10)    hydrogen gas take-off lines (20)    oxygen gas take-off lines (22)    array of individual cells (38)    electrolyzer apparatus (36)