That Whelen is tested every Saturday at noon. I heard it when I tried to record the P-50 in 2019. The P-50s are not active from what I was told.
Been planning on that for months now. I plan to hook up the STH-10 using the Thunderbolt's power source whenever get around to do it. Been working on a lot of siren projects (Modulator 6048, Model 2T, Thunderbolt 1000 control upgrades).