How does an emergency call actually find you?
Through several mechanisms layered on top of each other, because the original telephone network knew your address and the mobile network fundamentally does not.
On a landline, the answer is simple: the number is tied to a physical line at a registered address, and that address is looked up automatically. This is why landlines remain the most reliable way to be located.
On mobile, historically, the network could offer only the serving cell — which narrows you to somewhere between a few hundred metres in a city and many kilometres in open country. Calls were routed to the emergency centre covering that cell, and the operator asked where you were. When the caller cannot say, that gap is life-threatening.
What improved it. Modern handsets send a location derived by the phone itself — satellite positioning, combined with Wi-Fi network identifiers and cell measurements — automatically and only at the moment of an emergency call. The implementations are known as advanced mobile location and similar names by region, and they typically place the caller within metres rather than kilometres. The handset does this even without a data connection, using a text message fallback.
Other mechanisms worth knowing:
Emergency calls work without a SIM, without credit and while locked on most networks, and will use any available network, not only your own — which is why a phone showing no signal may still place one.
Emergency SMS exists for those unable to speak, and generally requires registering in advance.
Silent-call systems let a caller who cannot speak signal that the call is genuine, though the specific procedure varies and is widely misunderstood.
Internet-based calling is the weak point. Calls placed over Wi-Fi or an app may carry a registered address rather than your actual one — so keep that address current, since it is what the operator sees.
What3words and similar location schemes are accepted by some services and not others.
Procedures differ by country; check your own emergency service's guidance.