A magnetic resonance imaging system includes a split magnet system having a pair of MRI magnet housings separated by gap. The container is made of foil, which can be punctured by a mandrel. The resistance of the power supply line is lower than the resistance of the signal line. An output stage is connected between a first voltage rail and a second voltage rail. Combined recognition of audio and video signals provides for higher true alarm generation and lower false alarms level of the surveillance system.