my voip phone has a dial tone when it’s not even plugged in to the network switch.
as a matter of fact, it doesn’t even need to make a dial tone. it just does that because phones have done that since forever and people are use to it. it could just as easily say “please dial the number you wish to reach” when I pick it up.
The call does eventually leave the SIP (internet phone) network if it’s routed to a POTS number (plain old telephone system) though a local pop (sip to pots hand off) IF the call is going to a POTS customer. SIP to SIP never leaves the internet.
Copper is dying tech, that is why the giverment is dumping billions on LECs (local exchange carriers like Frontier and Centurylink) to provide “broadband” when they can’t even provide a dial tone to most of their areas now. They are simply trying to keep them (and their unions/donations) around.
(abbreviations explained for everyone as I am fairly sure you know what they mean already)
Thanks for sharing your knowledge.