PSTN - Public Switched Telephone Network

The Public Switched Telephone Network is the product of all regional telephony operators. Originally switching points routed calls however due to advances in technology now VoIP is used.  

The Public Switched Telephone Network is a system that enables telecommunication across the world. Made up of switching points at centralised locations originally interconnected using thousands of underground copper cables there has now been a shift to a digital network. This network joins people and businesses. PSTN lines have proven to be dependable over time even functioning during power outages and being less susceptible to cyber-attacks than digital networks due to their analogue technology.