lectric for leadership in the PBX marketplace. Other vendors jumped in too, with mixed success. Harris Corp. had some success with its Digital Telephone Systems product line, which, like ROLM, used a proprietary digitization technique. Rockwell International's Collins divi- sion built a large digital PBX system with specialized features for the automatic call distribution (ACD) market; it was popular, for example, at airline reserva- tion centers. An Illinois start-up, Wescom Switching, built a mid-sized digital PBX, the 580DSS, that made novel use of distributed control, dividing its tasks among several microprocessors. This turned out to be more of a programming challenge than its founders anticipated, though the 580 family found some suc- cess as an ACD. (Wescom was eventually purchased by Rockwell; its ACD busi- ness eventually evolved, under different ownership, into Coppercom, a manufacturer of small central office switches.) Japan's NEC also took a substan- tial market share. By 1976, AT&T was in a hurry to come out with a PBX that could at least begin to compete with the new generation of interconnect systems. A "feature race" had broken out, with ROLM and Northern in particular racing to come out with larger feature lists. This was possible because of their computer control; new features only required new programming, which could be applied to exist- ing machines in the field. Not prepared to offer a digital PBX of its own, West- ern Electric hurried to market a computer-controlled analog PBX family called Dimension [7]. These rapidly replaced the electromechanical PBXs in the Bell Operating Companies' lineup; although older models remained under tariff, they were no longer manufactured. In the terminology of the day, analog-computerized PBXs were called "second generation," whereas digital ones were "third generation." By 1978, the marketplace was cluttered with new computerized-PBX vendors. Digital machines controlled the high end, though analog technology remained The Rebirth of Competition predominan