POTS
acronymISP & telecomnetworking
Plain Old Telephone Service: the analog telephone network - a voice in the 300-3400 Hz band over a dedicated twisted pair for the duration of a call. Dial-up internet was data squeezed through its voice channel, one occupied line at a time.
The retronym the internet made necessary - and then made historical.
Plain old telephone service is the analogue line that carried voice for a century, powered from the exchange so it worked when the building lost electricity. That property is the one worth remembering, because everything that replaced it does not have it.
Its retirement is an ongoing infrastructure change with real consequences. Alarm panels, lift emergency phones, fax machines, medical alert devices and payment terminals were all designed against a line that supplied its own power and was assumed always present. Migrating them to IP is not a like-for-like swap, and the classes of failure introduced, most obviously that a power cut now takes the phone with it, are why the transition has been slower and more contested than the technology alone would suggest.
Also known as: plain old telephone service