NOVELTY - The system has a fuel cell with an electrolyte arranged between an anode and a cathode (4). A cathode path (6) includes a cathode gas guide (7) for supplying cathode gas to the cathode, and a cathode exhaust gas guide (8) for discharging cathode exhaust gas. An anode path includes an anode gas guide for supplying anode gas to the anode, and an anode exhaust gas guide for discharging anode exhaust gas from the anode. A compression device (25) for compressing the cathode gas is provided in the cathode gas guide, and selectively bypassed from the cathode gas by a bypass guide (28).    USE - Fuel cell system e.g. stationary fuel cell system, and mobile fuel cell system, for use in a motor vehicle i.e. commercial vehicle.    ADVANTAGE - The compression device is selectively bypassed from the cathode gas by the bypass guide, thus reducing exposure of the compression device to the cathode gas flow, and hence extending maintenance intervals of the system while achieving a maintenance-free system. The system accurately and dynamically adjusts pressure that is produced by the cathode gas in the fuel cell. The system exhibits an improved adaptation to pressure levels, a large freedom of use, high efficiency, and high customer value. The compression device is inexpensive, dimensioned small and subjected to less wear. The system is cost-effectively operated, and quickly and effectively provides response to change a required pressure level. The system is implemented in a simple manner with inexpensive components and reduced development and/or design cost. The system enables operating wide spectrum of different applications using less number of standard components, thus reducing application expenditure. The system avoids the need for charging assemblies and an afterburner, thus providing a compact system.    DETAILED DESCRIPTION - The fuel cell is a solid oxide fuel cell. The anode gas is hydrogen. The cathode gas is air. An INDEPENDENT CLAIM is also included for a method for operating a fuel cell system.    DESCRIPTION OF DRAWING(S) - The drawing shows a pneumatic circuit diagram of a part of a fuel cell system.    Cathode (4)    Cathode path (6)    Cathode gas guide (7)    Cathode exhaust gas guide (8)    Compression device (25)    Bypass guide (28)