Use voice domain for emergency call branding

To meet mobile operator requirements, OEMs can enable the voice domain to decide whether to use Emergency calls only or No service in the phone UI branding.

Constraints: FirstVariationOnly


  1. Create a customization answer file using the contents shown in the following code sample.

    <?xml version="1.0" encoding="utf-8" ?>  
    <ImageCustomizations xmlns=""  
                         Description="Use to let the voice domain decide whether to use 'Emergency calls only' or 'No service' in the
                                      phone UI branding. "  
        <Settings Path="Phone/PhoneSettings">  
          <Setting Name="UseVoiceDomainForEmergencyCallBranding" Value="" />
  2. Specify an Owner.

  3. Set the UseVoiceDomainForEmergencyCallBranding setting to one of the following values:

    Value Description
    0 or 'False' The OS inspects the registration state to decide the emergency call branding. This is the default OS behavior.
    1 or 'True' The voice domain decides the emergency call branding.

    If UseVoiceDomainForEmergencyCallBranding is set to 1, the phone will not display Emergency calls only in the following cases. Instead, it will display No service.

    • If the system type [RILSYSTEMTYPE] is NONE, which means there is no signal.

    • If the system type is LTE but there is no voice domain. This situation can occur in these cases:

      • In LTE networks being used by a non-VoLTE capable device without 3G coverage.

      • In forbidden LTE networks.

    However, if you do not set UseVoiceDomainForEmergencyCallBranding to 1, or the setting is missing, the device may display Emergency calls only in the above situations.

Testing steps:
Work with your mobile operator partner to test this customization on their network.

Prepare for Windows mobile development

Customization answer file overview