What was that tone that I heard twice in the video (after the whoops)?
the dong dong
I don’t remember where I saw this but I recall reading that WTC 7 had an older Firecom 8500 fire alarm panel, which would be the system that is heard in the video. I actually found the patent for this system a while ago and it explains the weird slow whoop/double chime tone.
[quote] Sound generation equipment, in accordance with the invention, incorporates both a whoop tone (pulsed siren form of sound) and a chime tone generator along with sequencing circuitry on a single IC (integrated circuit) card. [/quote]
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I found Firecom’s website, and indeed WTC7 has/had one of their systems.
[quote] With rapid growth and a unique corporate structure, Firecom has become a recognized leader in complex life safety, high rise, fire alarm, and voice communication systems. Our products are installed in such prestigious properties as the United Nations. The Waldorf-Astoria Hotel, [b]7 World Trade Center[/b], and Columbia Presbyterian Hospital. With the introduction of Life Safety Net 2000, we now offer this expertise nationwide. [/quote]WARNING: Read the post before watching the video!
Here’s one. This video is remarkably eerie. There is a 60hz or 120hz buzz in the background which I thought may have been an electromechanical horn, especially given how loud it was by the door. However, I think that the substation was also in WTC 7, so it could have also been that.
Warning: Starting at 0:23 it is revealed that there are people in the building, which may not have made it. In addition, at 1:41 possible screaming can be heard in the background, and at 2:39 a possible suicide may be heard. Either of these could be cutting equipment among other things, but viewer discretion is advised.
I’m fairly certain that this is the most graphic/disturbing video, and if the staff wishes, they can remove it, of course. If you do so, please PM me so that I can upload an edited version.
That is definitely a very sad video. 
However, I think that the tone heard by the door is most likely some sort of door alarm, since WTC 7 did have a voice evac system.
Definitely very gut-wrenching to watch those videos. I pray that all of the victims and the victims family have found peace.
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Here is a video that shows the emergency command center in the lobby of the North Tower during the collapse of the South Tower. As you can see, many of the lights on the panels were illuminated once the collapse began.
Please note, this video contains graphic and/or disturbing content, including the description and sounds (no visuals) of people on fire and of people commuting suicide. Viewer discretion is advised.
(The panel can be viewed at around 3:30)
Here is another, better quality version, which is less potentially graphic and disturbing than the previous video:
(The panel can be viewed at around 1:40)
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Both of those videos are sad videos 
The five men that carried this out need to be punished for all of the lives they destroyed.
Yes, but I believe they died in the crashing.
Ohhhhhhh boy…
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What? Am I misinformed?
There were alot more than 5. You need to study some history my friend.
Pretty sure they were punished with their death lol.
To bad they wanted to die for the “cause.” They feel they are with some virgins partying it up. Good thing we know that is not true.
The 5 plotters. The other hijackers were killed in the attacks. The five I was talking about were Khalid Sheikh Mohammed, Ramzi bin al-Shibh, Mustafa Ahmad al-Hawsawi, Ali Abd al-Aziz Ali and Walid Bin Attash.
Ah good work 
Just a reminder, this topic is supposed to be about the evacuation systems in the World Trade Center and in large buildings in general only. Please remain on topic.