Many moons ago, I had a Spectra siren in my fire vehicle. I can't tell you much about it, except that it was operated in conjunction with a smaller, specialty control head that was typically mounted immediately above the Spectra control head in the vehicle. The siren control allowed for the on/off and siren selection (manual/wail/yelp, etc) buttons and was connected to the other components with a multi-wire cable. And if you're not already aware, these high-powered sirens require specialized high-power siren speakers. A normal PA horn would likely be blown out instantly.