Per your linked article: "That began to change in the 1950s ... Following the D.C. Circuit’s Hush-a-Phone decision, the FCC began establishing standards that w

Per your linked article: "That began to change in the 1950s ... Following the D.C. Circuit’s Hush-a-Phone decision, the FCC began establishing standards that would allow the sale and use of myriad devices on the telephone network, from answering machines, to fax machines, to computer modems." The break-up didn't happen until 1982.