Synergy Teleconferencing System (STS) was a PC-based online chat server popular in the 1980s and 1990s. It arose as a replacement for the outdated Diversi-Dial system (DDial). Like DDial, it was a multi-line modem system that originally could handle eight simultaneous connections (later updated to handle sixteen), and using custom-produced RS-232 serial boards had a theoretical connection limit of thirty-two on an IBM PC-AT - type computer (80286 processor). While DDial was limited to 300 baud, STS was initially capable of 2400 baud speeds (later editions upped this to 14.4, 19.2, and 28.8). Using internal software, one or more of these lines could be used to establish links to other STS stations, effectively making the number of simultaneous users dependent on how many STSes were involved.