Abstract: The method serves for calling a substation (USm) by a central station (Z) in a transmission system for the purposes of information transmission by way of a communication channel (m) called from a plurality of communication channels. The plurality of communication channels is subdivided into communication groups (GRI, GRII, GRIII) of the same property or the same parameter values. Within a selected communication group (GRII) a communication channel (m) is called, which is still communication-free. If all (n) communication channels of the communication group (GRII) are already busy, the central station (Z) goes into a waiting condition until at least one of the communication channels of the communication group (GRII) becomes communication-free.

Abstract: A fuel cell assembly has an improved gas sensor. The improved sensor measures the gas concentrations in the interior fluid passages within a fuel cell assembly or within fluid passages employed to transport reactant fluid streams to or from the fuel cell(s). The improved sensor is particularly suited for use in the environment within the reactant fluid passages of a solid polymer fuel cell assembly and is tolerant to the presence of water. The sensor employs an active electrode; a passive electrode; and an electrolyte in contact with both electrodes. The electrolyte is disposed on a substrate and a heater is located in thermal contact with the substrate for heating the substrate and the electrolyte.

Abstract: A fuel cell assembly has an improved gas sensor. The improved sensor measures the gas concentrations in the interior fluid passages within a fuel cell assembly or within fluid passages employed to transport reactant fluid streams to or from the fuel cell(s). The improved sensor is particularly suited for use in the environment within the reactant fluid passages of a solid polymer fuel cell assembly and is tolerant to the presence of water. The sensor employs an active electrode; a passive electrode; and an electrolyte in contact with both electrodes. The electrolyte is disposed on a substrate and a heater is located in thermal contact with the substrate for heating the substrate and the electrolyte. In a preferred embodiment, the active electrode comprises platinum, the passive electrode is gold and the electrolyte comprises a layer of zirconium dioxide less than one hundred microns thick.