The invention relates to a fuel cell system (11, 111) comprising an anode chamber (13, 113) and a cathode chamber (14, 114) which are separated from each other by a proton conducting membrane (15, 115). When the fuel cell system is operated, fuel, in particular H.sub.2 or a water/methanol mixture, can be fed to the anode chamber and an oxidant, in particular oxygen, can be fed to the cathode chamber. In standby mode, the cathode chamber (14, 114) does not allow flow through and the oxidant and fuel are present in both the cathode chamber (14, 114) and the anode chamber (13, 113), respectively. The fuel cell system remains at operating temperature in the standby mode. This enables the fuel cell system (11) to be used as a combined interruption-free power supply unit and backup unit.

A fuel cell system with fuel cells displaying cooling channels assembled to form a fuel cell stack, with a coolant cycle in which coolant is circulated by a pump in a main cycle which includes the cooling channels and a cooler and with a heat storage unit and a heating device is characterized by the fact that the heat storage unit is arranged in a branch on the coolant cycle parallel to the cooler, that a heat exchanger that can be heated by the heating device is arranged in a second branch parallel to the heat storage unit, that a second pump in the first branch is arranged in front of the heat storage unit, that a two-way switching valve is provided which displays a first connection arranged in a first branch in front of the second pump, a second connection arranged in the first branch in front of the second pump and a third connection which is arranged in the second branch in front of the heat exchanger, and that a T connection is provided between the first branch, the second branch and the main cycle.

According to the present invention, access to a password area in a nonvolatile memory cannot be granted by simple supply of an address in a normal order. According to one preferable mode, for instance, a trap address is set in the password area so that reading information from the password area is permitted only when the password area is accessed without accessing the trap address, whereas when the password area is accessed the trap address, whereas when the password area is access through the trap address, information reading is inhibited, or meaningless data is output or the information in the password area is destroyed. This invention can make it harder to gain access to a password area which is used to protect against illegitimate copying and can provide a nonvolatile memory having a stronger copy protection capability.

A fuel gas and an oxidant gas are humidified using a flow transmitter and a static mixer to achieve saturation of fuel and oxidant process gases prior to feeding to a fuel cell.

A solid polymer electrolyte type fuel cell system having a reduced size and weight, which exhibits an improved efficiency. To supply reaction gas to an anode or a cathode, a water lubricated type compressor is employed with the following operational advantages. The face pressure of sliding faces of the water lubricated type compressor, that is the compression ratio and number of revolutions thereof, can be greatly improved, as compared to the conventional oil free type compressor. The compression efficiency is improved by reducing of leakage of reaction gas between the sliding faces. No oil film is formed so as not to deteriorate the battery performance. The size of the water lubricated type compressors can be greatly reduced to about one-third to a half of the conventional oil free type compressor. In addition, the improvement of the compression efficiency and reduction of the friction loss result in a great reduction of driving power. Hence, the fuel cell system with the present arrangement is practical particularly when used as a power supply for driving a vehicle, which is severely required to have a reduced size and weight and to be economical.