The New York City Fire Department dispatch tapes from September 11,2001.
Oral history files show that at least four channels were employed at WTC:
Channel 5, (possibly also called Command 5), was to be used for Command in both Towers.
Tactical 1 was to be used for Operations in the North Tower.
Tactical 3 was to be used for Operations in the South Tower.
Repeater 7, also known as Port Authority Repeater, was also used by some units working in the North Tower.
One officer said a channel named Command 3 was used for the North Tower. To those unfamiliar with the details of the FDNY system, it is unclear whether the interviewee meant Tactical 3 or a fifth channel.
FDNY personnel are seen using radios during the documentary footage of the WTC lobby area. Analysis of these scenes showed the radios all appeared to be receiving properly. Oral history files confirm radio communications were at least partly functional.