The Siemens 3RA1215-0JA15-1BW4 is a reversing combination starter in the SIRIUS family, frame size S00, built to IEC standards. It integrates a reversing contactor pair with overload protection in one compact unit that mounts on a FastBus rail — the SIRIUS bus system that distributes control power and signals across multiple starters without individual wiring. Rated for 0.7-1 A, it handles small reversing motor loads — conveyors, gate drives, or any application where direction change is needed. It ships with an MSP auxiliary contact (1 SPDT, NO/NC) and an additional auxiliary contact (NO), so you get feedback and status signals without ordering separate add-on blocks. That saves a slot on the bus and one line item on the BOM.
The FastBus system carries the control voltage bus along the rail, so all starters in a row share the same 24 VAC supply without daisy-chaining wires. The reversing pair is mechanically interlocked inside the housing, which prevents both contactors from closing simultaneously — a short-circuit hazard if they did. That interlock is factory-set; no external wiring or logic needed.