How does a mobile phone do emergency calls without sim?

The sim card only holds informations that the phone uses to authonticate to the network, the network checks if the user is registred with them and if he has credit then, allows him to make the call or not. For an emergency call, the network directly redirects the call to an emergency desk without checking your identity. Summery: you have all what you need to make calls on your phone not on the sim card