A system for perforating a well includes a perforating gun 10 and a swivel 12 suspended from a wireline 50. The electrical alignment mark set includes at least a top mark and a bottom mark. Upon approaching the support, a control indication is detected for initiating a further operating function of the electric hob as a consequence of the detection of said approach. A correct answer comparing unit 120 compares the category specified by the string matching unit 110 and a category of correct answer information 803. A first wall part and a second wall part are arranged at a variable distance from each other, said distance being defined by a differential pressure between the pressure of the charge fluid and the pressure of the fluid flowing in the flow channel, i.