Question: I have an Android Phone without a SIM card installed. This phone occasional receives/shows "Cell Broadcast" messages with numerical values only (no text).

Does anyone have a hint what that can be about?

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@cstrotm maybe they're the emergency broadcast stuff? A phone without a SIM can still communicate with the towers, but I am not certain what limitations exist. You can at least call 911...
@wend @cstrotm if they know your IMEI/IMSI or whatever, not based on the cell phone number right?

Yes. Triangulation by the Network provider. Or from some apps / the OS itself by measuring cell phone tower signal strengths on the phone. Then the IMEI would not even be necessary. But this is tricky and I do not know if google / Apple really do it.

@feld 911 would not do good here in Germany ;)

I'm also not worried, just curious.

All my other phones (Android, Ubuntu, iPhone) with SIM card installed don't receive/show the cell broadcasts. Only the one old phone without SIM card.

@cstrotm I thought a bunch of countries all begrudgingly accepted making 911 work and redirect to the correct local emergency services number (999, 111, whatever)

@cstrotm in poland the cell towers broadcast their location, in tve past I have seen the area code in a cell broadcast, sometimes cell tower id and antenna. There are different numerical 'channels' you can subscribe to.

@cstrotm cell broadcast messages are usually sent by carriers to any devices within range. They are commonly used by carriers for network info/updates (that may be nonsensical or irrelevant to you) and emergency broadcasts. There is usually a setting in Android phones to disable/mute these messages.

@vanzyl Thanks. I found tutorials on the net on how to disable cell broadcast in Android on SIM card level (for a certain provider). But in this phone, there is no SIM card and no such setting :(

@cstrotm if it's an android phone it will usually have a developer options menu you can unlock for more options. Might want to give that a try.

Go to Settings > System > About phone.
Tap Software info > Build number.
Tap Build number seven times to unlock developer options.

@vanzyl I've already checked the developer options, there is nothing about Cell Broadcasts there.

@cstrotm the plot thickens...🤷‍♂️

Godspeed my friend!

@cstrotm it could be one or a combination of several things, AGPS services, network survey, 911 services (IIRC sim free you can still call 911), just regular old channel control traffic.

@trox Leider nein, denn diese Anleitung spricht davon, wie man Cell Broadcast auf einer SIM Karte ausschaltet. Ich habe ja gerade keine SIM im Geraet, das ist es ja was mich wundert.

@cstrotm AFAIR, O2 uses Cell Broadcast channel 50 to announce a "Cell-ID". Swisscom for example uses channel 50 to announce the cell's location, e.g. "Zürich West". And in some countries (Netherlands?) uses it for flood alerts.

@Venty It might be the cell id.

I'm wondering why it started showing this messages in Dec2020, as I have this phone in the same configuration on my desk for over one year, and the cell broadcast messages suddenly started in December 2020. Sometimes many per day, then there are some weeks without a single cell broadcast message.

I've not put the phone in airplane mode, that should shut it up.

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