Tips for contacting 911 when the cell signal is marginal

[Joseph Elfelt]

This post is *not* for the purpose of debating whether one should carry a PLB.

Instead, if the reality is that you need to call 911 and you have a cell phone but reception is marginal, then here are some suggestions to help you increase the odds that you are able to communicate.

First, always try making a voice call to 911 even if your phone says there is no service.
Critical: Wait 30-45 seconds for the call to go through before hanging up.

The reason to wait at least 30 seconds before hanging up is because the call routing technology might try for first 17 seconds to connect to a cell tower for your phone’s carrier before trying to connect to any other compatible cell tower. For some background on this 17 second rule see:
https://transition.fcc.gov/Bureaus/Wire ... c99096.txt at paragraph 41.
https://apps.fcc.gov/edocs_public/attac ... -171A1.pdf

All wireless carriers are required by FCC regulations to carry all 911 voice calls as long as the tower and phone have compatible technology. You do not have to turn on any roaming for this to work. If your phone can ‘see’ a compatible tower for which your carrier does not have a roaming agreement then the phone will claim there is no service but you will still be able to call 911.

Second, try texting to 911.
Critical: Include your location in your text.

When you text 911 they will only know your location if you tell them! If you are in the backcountry then the best location data to send is latitude longitude in decimal degrees and the accuracy value for those coordinates. SAR responders might be skeptical of coordinates that do not have an accuracy value included.

There are over 6,000 PSAPs (Public Safety Answering Points) in the USA. Over 1,000 PSAPs are now accepting text to 911. Here is a link to a spreadsheet (updated monthly by the FCC) showing the PSAPs that accept text. https://www.fcc.gov/file/12285/download

A weak connection to a cell tower might still be good enough to transmit a text message while a voice call would fail to connect. But note that text to 911 *does not* use roaming. For this to work your phone must have a good enough connection with a cell tower owned by your carrier for the text to go through.

Third, try texting to someone that can relay your message to 911.
Critical: Be certain to turn on voice roaming before trying this step.

Normal texting *does* use voice roaming. (You do not need to turn on data roaming.) If your phone only has a weak connection with a ‘roaming' cell tower then you might be able to communicate by text but not voice. Of course this will not work unless you first make sure that voice roaming is ‘on’.

Tip: Do not send text to a group. Instead, each text should only go to a single phone number. Texting to a group might use a data channel instead of a voice channel. To have the best chance of success it is important that your text message use a voice channel.

Tip for iPhone: Turn off iMessage. This is a data service and requires more resources and signal strength. Turning off iMessage will ensure your text message is handled as a standard text using a voice channel.

But what if none of the above suggestions seem to work?

When the signal connection between your phone and a cell tower is extremely weak, the tower will ‘see’ your phone but not be able to connect a voice call or send a text due to the extremely weak signal. The good news is that the cell network will still make one or more data records for each of your attempts. No, these data records do not show your exact location. Instead, these data records can be analyzed by someone trained to do so and that information gets combined with other clues which then results in a “mostly likely” area for search responders to check. When you attempt to communicate as described above you just might be creating the data records that will be a crucial clue in helping the search team finding you.

[Aimless]

All good tips, but #1 is especially interesting to know. Thank you.

[squidvicious]

Another important point that I recall from when Portland rolled out text-to-911 service, which may or may not be true generally, is that they cannot process anything but plain text. Emoji, pictures, video, etc not only won't go through but can garble the entire message so that they won't even be able to read the text part.

It might seem helpful to send 911 a screen shot of your gps to make sure you're giving the right info without typos, or a picture of the injury you're calling for help with, but that will actually interfere with help getting to you.

[Joseph Elfelt]

Thanks for the tip about text only.
I will include that.

[Joseph Elfelt]

I decided to put the "Tips" for calling 911 into a pdf file and host it on my server.
Anyone who is interested will always be able to find the latest version at
https://mappingsupport.com/p/sar/smart- ... -phone.pdf

[Charley]

Good to know. Thanks!