Support for emergency voice calls
The Voice interface logic is updated as follows:
- The interface is available always, even in Failed (No SIM) or Locked (SIM-PIN locked) states.
- A new "EmergencyOnly" boolean property specifies whether only emergency calls are allowed.
- We load the list of emergency numbers programmed in the EF_ECC SIM file.
- We explicit forbid non-emergency calls while in emergency-only state, by following 3GPP TS 22.101.
The logic of 3GPP TS 22.101 is as follows:
- 112 and 911 shall always be available.
- Any emergency call number stored on a SIM/USIM when the SIM/USIM is present.
- 000, 08, 110, 999, 118 and 119 when a SIM/USIM is not present.
- Additional emergency call numbers that may have been downloaded by the serving network when the SIM/USIM is present (we ignore this on purpose in our logic, because if our network provides an emergency numbers list, we're no longer in emergency-only mode).