Whelen and Federal use a wail signal where the pitch never holds when it peaks. This could be good for rotating sirens that have a liner wind up. The old analog controllers that drive electronic sirens and sirens with series wound, repulsion induction, and universal motors have a pitch that peaks exponentially. A siren with a rapid wind up in the distance with an induction motor would peak and hold its pitch for a while, which could give a person the impression that the siren was running in alert depending on how far off into the signal they are when it swings their way especially if the siren is running on a 8 on 4 off timing. Knowing how fast a P-15 ramps up on 480 VAC the siren would hold it's pitch for up to 7 seconds. Multiple sirens in a system with this characteristic won't have this problem since the chance of the other sirens winding up and down while pointed their way is increased. Exponential wind ups have the advantage since they slowly peak and would keep people from getting that impression since the chances of them hearing the siren wind up would be higher. I personally prefer the 4/5 port 1000T over the Hurricane in terms of sound for this reason. 5 on 5 off works well with sirens with exponential wind ups IMO. This is how I wish Whelen and Federal would utilize wail on their controllers (it's a synth):
https://www.youtube.com/watch?v=YLOw_LME7Ss. I think that timing also would work well with mechanical sirens with linear wind ups. Now with omni-directional sirens it wouldn't matter. A 12 on 12 off fire signal works good on European sirens, because most of them were omni-directional. Uni-directional sirens that rotate... not so much.
https://www.youtube.com/watch?v=82A-lsOPlqo