Am 10.11.2017 um 15:24 schrieb Darac Marjal:
Its in fact part of the spec.
Part of the GSM authentication and network attach spec allows any device w/o a SIM, or without a valid SIM, to attach to the network, and will accept emergency calls.
E.g. If you have a T-Mobile phone, and occasionally see it in SOS mode, what's happened is that the phone can't see a T-Mobile tower, and connects to an AT&T tower instead. There's no roaming agreement, so AT&T won't let the device onto the network, but will accept SOS calls.