A particular problem that results in many 911 hang-ups was never mentioned in the June 13 Triangle Trouble Shooters article. In many corporate environments you are required to dial 9 to get an outside line. If you then intend to make a long distance call, you dial 1, followed by the number you want to reach. This is fine at work, but not at home.
When at home, if you forget and dial 9 followed by 1 for the area code, you get a message telling you that you have made a mistake. You then hang up. This last hang-up is interpreted by the system as a the final digit of 1, and, without even knowing it, you have dialed 911.
Over the years, I personally have had at least two visits from the city police asking if everything was OK. I have had at least three call-backs from 911 asking the same question. In every case, I had not intentionally dialed 911, but did so accidentally because of the requirement to dial 9 for an outside line at work. I simply forget that I was at home and no 9 was required.
This is the explanation for many 911 hang-ups.