How does Reverse 911 work?

In what has become a national news story escaped (now recaptured) murderer Danelo Calvalcante was on the loose for two weeks. There were news articles that ‘the authorities’ were using reverse 911 calls to a) tell people to lock doors, secure outbuildings (barns & sheds), & be vigilant) & b) notify them of his capture,

How do they work? Wikipedia states that it uses billing address of your cellphone.

Back in the old days, when people had home phones, with fixed locations they’d call your house & leave a message on your answering machine (remember those) if no one picked up. However, with cell phones, billing address doesn’t necessarily match up to location -

  • I’m on a family plan with her, as is a kid hours away in college. Neither the kid or I have a cell phone registered to our address.
  • I know of two people who are full-time RVers, one who spends considerable time living in other’s houses, a week or so at a time, pet sitting while the owner is on vacation.
  • In terms of online billing, I’m sure there are a lot of people who have moved & haven’t updated the address with the cell phone company because they didn’t think about it with getting their bill via email.

In short, I’d expect a lot of people wouldn’t get the very important message if they are using billing address.

Can they narrow those messages down to a tight location; weather alerts I’ve gotten seem to be more region wide than a neighborhood or two so could they use phone location? In that scenario, what happens if I’m not in my neighborhood when they send the message out. If I’m at work out to dinner, or a concert or ___ would I ever know there’s a killer on the road (& that his brain is squirming like a toad)?

I think they are using the emergency alerts system that blasts a message out to every cellphone, except that it’s more targeted. Probably they are just picking up the ZIP code from the billing address, and then sending the message to every phone registered to the relevant ZIP codes.

I’m sure for the reasons you state it’s not 100% accurate, but probably >90% accurate. Perhaps you’re making the perfect the enemy of the good?

I suppose a better system would be if the emergency alerts system could blast a message to every phone that’s connected to any cell tower in the relevant area. Perhaps there’s some technical reason that doesn’t work.

That is how the emergency alert system works.

The alerts are broadcast to the geographic area affected by an emergency. This means that if an alert is sent to a zone in New York, WEA-capable mobile devices in that zone can receive the alert, even if they are roaming or visiting from another state. In other words, a customer visiting from Chicago would be able to receive alerts in New York so long as the person has a WEA-enabled mobile device in the alert zone.

It does seem a bit odd then that Reverse 9-1-1 doesn’t use this approach.

Perhaps the aim is to target residents, and deliberately exclude people with cellphones who are present but do not live in the area - which could include the escaped convict himself? But I would think it would be more important to get the message to everyone, it’s not as thought the escaped convict is really learning anything useful from a message telling people to lock their doors and be vigilant. I suppose he’s learning that the area he’s in is part of the area where the police think he might be.

Many city & county governments have alerting websites. You have to sign up for it, and then they will send emails, texts, or calls to whatever address(s) you provide.

These sites also typically have lots of categories of alerts. Notices of city council meetings, trash pickup disruptions, and yes, real police or natural hazard emergencies.

I live right near a county line and both counties use this alerting platform:

Side note from my previous years working for T-Mobile. This is one of the reasons your carrier wants you to update your e911 info on your account, especially if you use wifi calling (using local wifi instead of the cellular network to call, especially common in areas where you may not have good signal).

From the section on updating your account information from their website:

An E911 address allows emergency services to determine the location of each phone or device, in case they need to call 911. Wi-Fi Calling and some other T-Mobile products require a valid E911 address to work.

It’s not perfect of course, but it’s a good idea to update with your carrier for just-in-case.