All of these are cpv-90s which would have most likely been in the twin towers before 1993. These panels piggybacked off an xl3/system 3. The cpv-90 was basically the pre mxl-v released in 1984. And also the 9/11 pa message video actually used this tone on the fire panel: Pyrotronics CPV-90? - #2 by randomperson this message is the same message that the cpv-90 uses.
According to the very first post in this topic the WTC’s original system was an “American Multiplex”: as far as anyone knows Cerberus Pyrotronics did not become involved panel-wise until 1993 when the system was upgraded.
But it says the building contained a pyrotronics cr-7 system though we don’t know much about the cr-7 I remember finding out somewhere that the cr-7/xl-3 are the panels that the cpv-90 piggybacked off of
It’s semi-well known going by the comments on the video (the original may not have gotten much attention but now that it’s been reuploaded more people have likely seen it now that they’re aware of its existence to begin with).
Could have considering the original pre-1993 WTC 1 & 2 system used bullhorn-type speakers (at least if that’s what you mean by “paging speakers”).
Yeah, which according to what others have said is used to notify building occupants that the fire department has been notified: the reason it might not be sounding on the above system could be due to several reasons, including the feature being disabled (if it’s possible to do so on the 8500 at least), the system not being connected to the FD & thus having no reason to sound the chime, it not having notified the FD at that point in the video, etc.