PSTN

The public switched telephone network is the name given to the wider telephone network used to make calls locally and globally that is independent from the internet. If you have a home telephone then it is likely that you make and receive calls via the PSTN that your phone connects to via a port in the wall. Some businesses still use old fashioned PSTN lines where each phone has a set phone number and line, though this is considered redundant technology and will be phased out by 2025.