This a topic listing and discussing repowered sirens. Repowering refers to rebuilding a piece of equipment (such as a siren) with a different engine/motor/controller.
One such example is the repowered Federal Electric Type B at Shandon Ohio. (credit to 4j25). Note the new motor mounted in the box next to the siren.
https://www.youtube.com/watch?v=ZQvGGPMHM2Y
I also learned the 1212 prototype near my grandparents got repowered with a UV controller. (credit to 4j25) Note the new black drivers.
https://www.youtube.com/watch?v=BFDK1EhvBCw