e carried over separate trunks [32]. Pricing was a differ- ent question! Although most European PTTs treated all ISDN circuit-switched calls, either voice or data, at parity with analog calls, most RBOCs viewed ISDN as a premium service, subject to higher usage charges. In particular, almost all residential analog telephone service was offered at a flat rate (no usage charges for local calls), a situation that the RBOCs were not necessarily happy with but which regulators and, in some states legislatures, insisted upon. ISDN was seen as a way to impose measured usage on residential subscribers. So RBOCs often offered residential ISDN at measured rates, whereas analog lines could use modems at flat rates. This was a powerful disincentive to ISDN and sent a clear message to potential users. ISDN calls within a Centrex system-which could often be deployed on a LATA-wide basis-carried no usage charge. Some com- panies did create ISDN centrex groups for telecommuters and some Internet service providers did make use of Centrex and similar specialized services. But ISDN was usually not positioned as a substitute for plain old telephone service. Not all states accepted this. California, with its large technology commu- nity, struck a compromise; Pacific Bell's residential ISDN usage was metered during the business day, not at night. Tennessee ordered BellSouth to provide unmetered ISDN at a very reasonable rate (under $35 per month), roughly half The Great Telecom Meltdown the unmetered rate in other BellSouth states, on a statewide basis. For a time in the early 1990s, before the Internet was available to the public, that state had its own ISDN subculture, with dozens of bulletin board systems using ISDN. Some of the NYNEX and GTE service areas had unmeasured ISDN "voice" usage and measured "data" usage. Since the intraLATA network almost always carried voice in a manner that could carry data on a 56 kbps basis (i.e., 7 out of 8 bits), "data over voice bearer service" became a popular option supported by many equipment 