The system reaches out and 'polls' the network, looking for the respective connected/device associated with that phone #. If no return signal is received by the network/system provider, it goes to VM for the caller. The system cannot connect to a phone that is not turned on(!)
So I've noticed that when calling blocked or unavailable numbers, the phone does one ring and then states that the number is blocked or unavailable. This, I'm assuming, is because the initial ring is the phone connecting to the PSTN, and it is only after the phone has connected to the PSTN that it recognizes the fact that the number is unavailable or your phone is blocked, etc.
However, I've also noticed that when calling a dead phone (no battery), the phone goes directly to voicemail. My question, then, is how does this happen? Am I getting something completely wrong here, or does the phone have a way of instantly recognizing when another phone is dead?