The Siren Board

Good morning, I have been watching Sentry siren videos on YT and I noticed that on the single phase models, single tier sirens, that when the siren is in wail mode it has a sudden slow down then winds back up throughout the cycle, now I know about capacitators but can somone on here dummify it for me? how does it do that from way down there when the motor is up on top of the pole

As the siren winds up the start capacitors discharge, in order to charge them back up for the next use, the siren charges them back up during the wind-down. There is a centrifugal switch on the motor so when the siren hits a certain RPM, it turns the motor into a generator to charge the start caps back up again. That is why it has a sudden wind-down. I hope the explanation helps!