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.

In the many years I have been in the telecommunications and technology field one misunderstanding seems to continue to be prevalent, that...