For implementing an emergency call system between a telecommunication device and an emergency call center, the telecommunication device includes a log-in and log-out state via a switchable log-in function at a VoIP telecommunication service provider via an IP infrastructure consisting of at least one router. The emergency call center has a public IP number via which, in the log-out state of the telecommunication device, an emergency call connection diverting to the VoIP telecommunication service provider is safeguarded between the telecommunication device and the emergency call center.