An acronym for the public switched telephone network. The worldwide network of switched telephone interconnections, enabling hundreds of millions of telephones worldwide to establish direct connections. Originating in 1876 with Alexander Graham Bell’s patent, It began with a number of local, manually switched analog networks, which were gradually interconnected as standards emerged. By the 1950s and 1960s, most local switching networks had made the transition from manual switching, which requires a human operator, to electronic switching, which enables direct dialing. In the industrialized nations today, much of the switching network employs digital technology, with the exception of the local loop, which is still primarily analog due to the antiquated wiring found in older homes.