Originally posted by ev607797:
[b]To protect the paper insulation from obvious destruction in the event water enters the cable, this type of cable is pressurized with nitrogen. Pressure sensors are placed at various points along the cable route to monitor this pressure. In the event of a pressure drop, an alarm is sounded in the central office for immediate repair.
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Well since you brought it up Ed. Actually the air pumped into the cable at the CO end and also in huts to re-supply the air was plain old compressed air ran through dryers filled with desiccant. When you had a leak or a dryer went bad you put on tanks of nitrogen, one of the reasons you always vented a manhole before going in, nitrogen won't support life. The pressure contactors rang into a board and would place a short on the cable pair, you'd read the resistance on the short with a wheatstone bridge to determine which contactor was in alarm, of course you could only read the closest one in alarm. Also from my old splicing days, can you guess how much (percentage) of cable (air core) is used for air flow? You won't believe the answer. This might make a good question for the trivia.
