A solid oxide regenerative fuel cell system is used to supply power in a fuel cell mode and to generate metabolic oxygen and a hydrocarbon fuel reserve in an electrolysis mode. Apparatus for administering medical gases is also disclosed including a housing, a cassette associated with the housing containing at least one compressed gas cartridge preferably containing at least an amount of the medical gas substantially as required for a single dose and a patient supply interface to provide the medical gas to the patient. The current components are added together by a summing amplifier so that a signal corresponding to a tristimulus value is composed and then converted into a digital signal. The system may be used for interconnecting or communicating between two or more components connected to an interconnection medium within a single computer or digital data processing system.