IP, but sometimes ATM or even TDM. But then it also came to refer to switches whose internal software had hooks and handles for customization, or even switches whose software was only partially complete, by design, SO that original equipment manufacturers (OEMs) or carriers themselves could develop customized solutions. These were both in marked contrast to the monolithic model of older switches, whose extensibility, other than vendor-supplied features, was usually limited to the Intelligent Network capabilities defined by Bellcore. These two categories of softswitch were not mutually exclusive; some of the new switches were not only extensible but had internal architectures that visibly included both a call agent capability (a software application) and a media gateway (the switch backplane and its interface cards). Most new switches did, in fact, consist of a call agent and a media gateway, but then SO did a 1930's vintage crossbar switch. Eventually, even legacy switch vendors took to calling their products softswitches, but the term mostly stuck to the new generation of switches that was to arrive on the market in the late 1990s. The CLEC Boom and Bust Led to Glut of Vendors Quite a few central office switch vendors-almost all of who could call their products softswitches-started up or entered the market during the boom. One of the first CLEC-oriented switch vendors began as Digital Telecommunica- tions Inc., before changing its name to DTI Networks. It could trace its heritage back to a mid-1970s PBX start-up, Wescom Switching, but by the 1990s it was a small manufacturer of specialty call distributors based in Tennessee. After the Telecom Act, it rolled out a primitive but inexpensive "tandem" switch, the DXC, which was suitable for PRI offload. Dozens of ISP-CLECs bought them. By 2000, it had moved its headquarters to Florida and merged with DSL equip- ment vendor Coppercom and taken that company's name. This was a timely bailout for Coppercom shareholders because its core market, SDSL, was CLECs Winning St