I'm not completely up to snuff when it comes to electronic sirens, but I believe "pre-864" is the WS-3000 controller, similar to the early WS-2000 controllers. I believe these are pre-1984, and are exceedingly rare; imfamusly used in Puyallup's old system.
@@MidwestSirenProductions I think what he should've pointed out is that this is using a non-microprocessor decoder controller which are the first generation on Analogs. The ESC-864 (second generation analogs I would call it) didn't come out until 1986 which than, is when Whelen renamed from WS into WPS.