echo, who knows what's up with the arrays. I've always figured Federal doesn't make the DSAs but buys them off someone else (Atlas?) and resells them. The DSA is such a simple design it would make sense. I figure ATI did the same thing and purchased from the same manufacturer. I don't figure Federal would happily sell its equipment to a competitor to reuse!
You know...darn good question you raised with the Class D amps, Mysterious. Time for some total speculation on my part (can ya handle it?

). I'm going to pull all sorts of information from this thread I posted, so catch up if you need to:
https://airraidsirens.com/forums/viewto ... =2&t=15184
ATI filed both its patents for using a Class D amp in early warning siren systems in 2002. My guess is that they had tried it out before then, given they were making sirens before 2002 (but my hunch is probably not long before 2002, given the relative scarcity of the pre-Kingstar ATIs). Mind you, the Nashville ATIs had the same MCP-style boxes as are seen on the Atlas ATIs, so my guess is same electronics, different speakers.
Now, that being said, if you note in my thread I post a picture of an ATI amp from an eBay auction, then later show modern ATI boxes. The modern ATI boxes use amp boards directly inside the cabinet seemingly a part of the control board whereas the 1600 watt HPSS amp seen from the auction is modular in nature and totally self-contained. Both, however, seem to share the same layout corresponding to a Class D amp.
My hunch (and its only a hunch) is that the amp seen on eBay is from an early MCP style ATI cabinet (be it from a Kingstar or Atlas system) and that the MCP-style cabinets used some kind of modular design similar to what Federal was doing at the time (notice the connector to a mother board on the back of the eBay amp). I would figure you can hook less than 1600 watts into a 1600 watt amp, even though our Atlas ATI exemplars feature either 4x 400 watts or 2 x 800 watts (both getting us to 1600 watts; its also hard to see what's going on with the Baytown example). Furthermore, I think this means that ATI indeed used a 1600 watt Class D amp from day 1, but changed it from a modular model to a board sometime along the way (likely when they began using their own cabinet design...perhaps as a reason for their current design). I also believe that ATI has used the fact they use a Class D amp as a differentiator from day 1. Whether or not the D amp for outdoor warning is what switched them from a consulting firm to a manufacturer is a matter of deeper speculation that I won't get into, but there is some convincing evidence in that direction.
*end speculation*
I wonder if this helps you along, Mysterious.
I also have an update from earlier.
TboltTX1 wrote:
The only other possibility is that the Bayer refinery itself had Whelens, but that's very skeptical given that the closest siren location to the person who filmed the video is Holloway Park, which is on the other side of town from Bayer. So if this is the case Frisco, Texas was not the first instance of ATI using Whelen's tones.
I also did a little more digging I should have done earlier. The poster of the above video seems to later confirm there's Whelens at Bayer in the form of 2700s (though the OP seems confused about what they are; given there's a high pitched analog 864 whoop, I figure its probably a 2700).
Source:
http://www.youtube.com/watch?v=w2SnhS-btq8