 "protective coupling arrangement" from the tele- phone company. Such devices rented for several dollars per month per line, making them uneconomical for simple applications such as home telephone lines, but they created a mechanism for the competitive deployment of business telephone systems, such as PBXs and key systems. One form of coupler, the data access arrangement (DAA), opened up the network to a competitive supply of modems. Of course the Carterfone decision itself also deregulated the use of acoustic couplers; such modems, which did not need DAAs, were very popular in the 1970s. Registration Opened up the Floodgates Several years after Carterfone, the FCC took the next step in opening up termi- nal equipment competition by removing the requirement for protective cou- pling devices. Terminal equipment registration instead allowed manufacturers to have their gear certified for direct attachment [2]. At the same time, telephone companies were ordered to adopt the new "modular" connectors; these would become the standard subscriber interface. Registration did take some time to work its magic: Testing laboratories were initially backlogged, and many devices were sold under the "grandfather clause" that waived registration for any device that any local telephone company had deployed prior to the registration deadline. With the customer's ability to connect its own "terminal equipment" to the network, manufacturers unleashed a wave of innovation. Some existing products moved from telephone company rental items with low volumes and high prices to high-volume, low-priced necessities. The lowly answering machine, for instance, had been rented under tariff to a handful of businesses that really needed it; for example, movie theatres that used it to announce their schedules. Once customers could buy their own, they became almost a house- hold necessity. This increased the percentage of calls that were answered, improving telephone company revenues. The Rebirth of Competition Digitization from the Outside In Does de