“SOS” is on because the device or system is in some kind of distress or emergency-only state.

What SOS usually means

  • On phones (especially near the signal bars), “SOS” usually means there is no normal network, but you can still make emergency calls only.
  • In general, SOS is an internationally recognized distress signal meaning urgent help is needed.
  • It is not originally an acronym, but people often treat it as “save our ship” or “save our souls” in popular use.

If you meant your phone

If this is about your phone showing “SOS”:

  • It likely has lost regular carrier service and can connect only to emergency services.
  • Common reasons include:
    • Being in an area with poor coverage
    • Temporary network outage
    • SIM card issue or account problem with your carrier

If you tell what device (iPhone, Android, something else) and where you see the “SOS” text, a more specific explanation can be given.