Alertus is a company I found out about just a few weeks ago. They do mass notifications with a number of products from in-building systems to outdoor warning sirens and text-to-speech software. They also can integrate their products with existing systems from a few different companies like Whelen, ATI, FS, ASC, Cooper, and probably a few other companies not mentioned on their site if they get requests to do it. The interesting bit, for me anyway, is their sirens themselves. They are using what sound to me like a Telegrafia (German siren manufacturer) controller to drive their them, and they apparently source the speakers from the same company as Cooper, Telegrafia, and SiRcom with the company name on the sides of the horns. In attack/fire they run and peak at 415/425 Hz. Cooper's WAVES sirens by comparison are dual tone but peak at 850/1020 Hz like a dual tone UltraVoice panel. Since the Hörmann ECN and ECI series sirens aren't sold in the US (the ASI site itself is actually down currently) that makes this brand and SiRcom USA the only manufacturers in the US that sell sirens with that tone configuration.
Link: https://www.alertus.com/alertusproducts/hpsa
In the link there is a link to a demo of it running with a chime and voice. The chime is the some one used on the Telegrafia Pavian series sirens in Dresden, Gremany, except it's slightly lower pitched.
You can hear one running in attack at around 13 minutes in the video. It cycles with a 10/8 second on/off timing. With dual tone sirens like this that peak at almost the same pitch, the only thing that sets them apart is their ramp ups and wind downs. This one ramps like a Pavian siren - compare it to this one: https://www.youtube.com/watch?v=EeyMEbfkRZA
https://www.youtube.com/watch?v=O69qZu6QPZM