during the maintenance phase in fig1 another switching device is provided which is formed of a field effect transistor t 2 a diode d 2 which connects the output toward ground of the field effect transistor t 2 to the end toward the supply voltage of the coil l and a gate trigger circuit gt which triggers the gate of the field effect transistor t 2 on the specification of a trigger signal g 1 on the input side a voltage u_boost is applied to the field effect transistor t 2 in the exemplary embodiment this voltage amounts to 60v and is furnished by a capacitor cb this first switching device serves to subject the coil l of the solenoid during its attraction phase to the voltage of 60v which is markedly increased over the operating voltage the voltage of 60v increased compared to the operating voltage is generated according to the invention by a booster circuit which in response to a corresponding trigger signal or booster signal b_in generates an output voltage of 60v over a predetermined period of time from the operating voltage this output voltage charges the capacitor cb acting as a buffer memory with a charge quantity that is dimensioned such that during the attraction phase the coil l can be supplied with sufficient current or sufficient energy the booster circuit generates the increased voltage by means of a resonant circuit comprising a booster coil lb and a booster resistor rb this resonant.