> > in pressurized conduit - I fully believe some paranoid TLA's use 400PSI > > and a pressure-drop alarm as a deterrent. I keep hearing rumors that > > involve 400PSI nerve gas, and I'm not sure if anybody is THAT paranoid. ;) > > It does not take 400 PSI, it just takes a couple more than atmospheric, > and the really nasty sensors are not looking just for breaks, but for > any pressure differential, such as caused by bending, moving, etc... > buts thats mostly for fiber in 'secure' installations. Yep. I've installed one network that was run in pressurized conduit. It wasn't high-pressure, but the pressure sensors were connected to an out-of-band dedicated network inside the conduit, and the pressure varied randomly over time. All the sensors had to read basically the same pressure as was being applied at that time, to keep the alarm from going off. This was just one element in an overall atmosphere of utter paranoia, so it didn't seem all that crazy at the time, about ten years ago. I thought it would yield lots of false-positives, but surprisingly, it didn't, and it was actually pretty good at pinpointing the location of any breaks or blockages, relative to the sensors. Ridiculously expensive. -Bill