The M2 sends a low voltage 12-24v to that Siemans auxiliary contactor. That coil pulls in and powers your pump. The Rainbird will work the same way, send low voltage signal to auxiliary contact. If they are both 12v, M2 and Rainbird, they can go to Siemans contactor. I can explain it better in person or phone. 864-590-3681 if needing more info.