"Reverse 911" ???

I see mention of the use of a “reverse 911” system to warn residents about some danger. What is this? How does it work? How is it different from just calling people on the phone?

You can call 1000s of people on the phone all at the same time, playing a recorded message. Usually it’s either for the citizens to evaculate (e.g., tanker truck leaking hydrogen on the interstate less than a mile away) or stay in their homes (e.g., murder suspect on the run from the cops).

That puzzled me at first, too. What I think it refers to, though, is the fact that a modern 911 system can quickly link phone numbers with street addresses. So, when you call in an emergency, you don’t have to tell them where you are. Now, to turn it around, let’s say you need to warn everybody within 3 blocks of such-and-such a place about some danger. That same system could quickly cough up the phone numbers of everyone living on those streets.

Sounds like combining my answer with Jake4’s is the ticket - the system can quickly determine what numbers need to be called, and then it can be set to call them all automatically, to play a recorded warning message.

Interesting. In my locale “reverse 911” only refers to the ability to locate the caller, which is a bit tricky when a cell phone is used. Never knew that other places had another meaning.

Just to give some context to the question here is a link:

Bulldozer rampage gunman dead

Normally, that’s called enhanced, or e-911. It’s extremely useful in cases when someone dials and just yells “HELP!” and hangs up. As soon as the call is in the operator’s ear, the address is on their terminal. If someone yells “HELP!” and the line goes dead, they generally dispatch cops code 3 to that location as increasingly, such calls are from someone under attack in their home.

Back to reverse 911 - I used to leave near some oil refineries, and the system was simply referred to as the “emergency notification system.” More often than not, it didn’t work right. Something goes boom at the refinery, and the next day, it’s all over the news how the system didn’t call anybody.