Voice evac panels that would have been in the twin towers pre 1993
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.