Memory just popped up, back in the 60s the Sheriff was moving lights onto new cars coming on line. Stingy Albert invested in some 4 light rotating beacons and had the mechanic mount them on roofs and put the old sirens behind the grill.
Funding ran a little short so the mechanic dug into his stash and found a box of Cole Herse heater switches, 6 volt with the resistor built in to act as an indicator lamp. It worked, pretty much, until Deputies learned they could dial the beacon down. Somebody in comand thought it was a great idea, since rotation at different speeds got more attention. Somebody else figured out running a second wire to keep the light full on while rotation ran at whatever.
I said absolutely nothing to keep from volunteering to help the "mechanic".
Maybe a year later Sheriff's radio comes alive with a Deputy in heap big trouble. They'd beaten the motors near to death running em slow, and a lot of guys developed the habit of reaching over to punch the roof and get the light rotating. This guy used the heal of his hand and learned he was attached to the roof with about an inch of sheet metal screw. He was also no longer in position to drive the 3 on the tree Chevy Biscaine.
He rode to the hospital sort of holding a chunk of roof with flasher base attached. Took quite a while for the hand to heal so he could shoot.