From the 1990 AT&T educations series about telecommunications. This segment is about the PTSN (Public Switched Telephone Network), PSDN (Packet Switched Data Network) and The Cellular Mobile Network (AMPS). Sourced from VHS.
"Clearly, the Public Switched Telephone Network is the heart of telecommunications." Well, it was, anyway. I'd focus on that Public Packet Data Network if I were you.
