To provide a small-sized fuel cell system capable of providing a mode having a simple constitution preventing power generation of a fuel cell in an overload state, preventing a deterioration in the fuel cell system and providing a stable output from the fuel cell in the fuel cell system constituting a power source by the fuel cell. The connector receptacle includes integral alignment features for mating with the connector plug upon insertion of the battery pack into the electronic device. The microtoroid optomechanical oscillator can be fabricated from a silica-on-silicon wafer. Pixels on the touch sensor panel are formed by the unique pairings of individual drive electrodes and their adjacent sense electrodes.