system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 : Regarding the current event surrounding the missing Malaysian airplane, if family members of its passengers claim that they can still call their missing relative's phone without getting redirected to voice mail, why doesn't the authority try to track down these phone signals?

Are there technical limitations being involved here that I'm not aware of? Assuming the plane fell into a body of water somewhere, I'm sure you just can't triangulate onto it like in urban settings (where tons of cell phone towers dotting a relatively small area), but shouldn't they be able to at least pick up a faint noise and widen their search in that general direction?
gpt
Phones don't really work that way.  When you dial a phone number it's sent to the telco.  The telco could choose to send you a ring tone while it's attempting to locate the phone.  Unable to find the phone it can just send you to voicemail which is located at the telco not on the phone.

Just because you hear ringing isn't a promise that the other phone is actually ringing or reachable.

Alternatively the telco can just sit there and play ringback tone forever because thats how it's configured.  None of which is a promise that it can reach the phone.