Thor is a 200 watt siren amplifier that powers two 100 watt speakers. Airhorn, wail, yelp and a combination of wail and yelp are on call with the Thor siren. When the siren is turned on you will hear wail from both speakers by hitting the horn the tone will change to yelp. Hit the horn again and you will get wail from one speaker and yelp from the other. Hit the horn again and you are back to wail and can start over again.