Siemens sirius contactor 3rt1 series siemens 3rt1015 1bb42 the siemens 3rt1015 1bb42 is a sirius contactor from the 3rt1 series this switching contactor is the most commonly used switching device in industry mechanical engineering and in switchgear and control gear due to the increased automation in manufacturing this type of contactor has become more important this has also increased the variety of loads that must be controlledautomated production systems are considerably more sensitiv