it had not been pushed. On the audio track, an outside agency, possibly in New Jersey and using a repeater, comes through the receive audio on the Port Authority Repeater 7 system. An ambulance being dispatched by the outside (non-FDNY) agency is heard. This may be what the FDNY had described as interference caused when the repeater was left enabled at all times. The distant user appears to be repeated through the system, (possibly on the same CTCSS tone as was configured in Repeater 7). This appears to be a distant co-channel user on the same input frequency as Repeater 7. It's possible that by the random button pressing, a user sent a function tone that temporarily put the base station in monitor and that's what caused the outside agency's traffic to be heard. This is unlikely because subsequent transmit function tones should have toggled the receiver from monitor back to CTCSS-enabled. Fire Department system An oral history interview revealed the Port Authority UHF radios were normally used at incidents inside the World Trade Center. The interviewee said in normal, day-to-day calls, the WTC staff handed Port Authority UHF radios to firefighters on their arrival and that these radios, "worked all over." This implies, but does not prove, that it was common knowledge among department members that FDNY radios had coverage problems inside the buildings. The 9-11 Commission uses the phrase, "performed poorly" to describe FDNY radios during the incident. 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. A problem that shows up in these types of incidents is that