Abstract: A power circuit comprises a current amplifier circuit connected between a minimum potential line and a maximum potential line. It further comprises, connected between these lines together with the aforementioned main circuit, a protection circuit which has a control input. A trigger and distributor circuit is connected in parallel with these circuits and is adapted to neutralize the protection circuit, via its control input, when the voltage across the main circuit is below a threshold value. Is it also adapted to activate the protection circuit when the voltage across the main circuit reaches this threshold value, while maintaining the voltage across the main circuit at an approximately constant ratio to the voltage between the two potential lines. The circuit is applicable in particular to controling failsafe alarm circuits, by means of logic signals, for example.

Abstract: A method and a device for determining explosivity rate of a gaseous medium with a detecting filament which is heated in said medium by an electric current flowing therethrough. Said detecting filament is ignited through connection to a power supply and power supplied to said filament is regulated so as to maintain constant the resistance thereof. At some successive moments value of a quantity U significant for power supplied to said filament is taken into account. An exponential curve is extrapolated from such values; parameters thereof are identified and introduced in a process function adapted to deduce therefrom an estimation of the initial explosivity rate of said gaseous medium independently of the nature of the explosive gas(es) present therein.