A signal conditioner for use with a controller and a burner receives an input signal from the controller. The valve includes a valve head and a valve seat, in which the valve seat is arranged in force-transmitting connection with a membrane, whereas the valve head is fixed to the remaining structure via at least one stay. The plug unit engages the receptacle unit housing socket contacts within closed, nested, oil-filled chambers. Further, the dirt separator provides a convenient surface for mounting a pressure sensor. When the driver unit is rotated, the switch lever is released from the press of the guide pin and the detection switch is turned OFF, thereby cutting off the power.