For decades, DSL and POTS (Plain Old Telephone Service) over copper lines have been the backbone of phone and “last-mile” internet service in the U.S. But now, national telecom providers like AT&T and Verizon, under shifting FCC rules and dwindling demand, are planning to retire these services. That means businesses still relying on copper lines—even for “just a few” analog phone lines, elevators, alarms, security systems, or fax machines—need to plan for a transition.

This is an industry term that has been around for a long time. POTS stands for Plain Old Telephone Service. This specifically refers to...