The invention relates to a device for switching on and off an electric circuit comprising: a charge (5) which can be ignited, the combustion of which brings about the switching on or off of the electric circuit, ignition means for the pyrotechnic charge (5), characterised in that: the ignition means are connected to the electric circuit and the ignition means comprise a microswitch (M, M') with magnetic action for controlling the ignition of the pyrotechnic charge (5).