技术在快速发展进步。因此，我们建立了易于使用的术语汇编，帮助您更好地了解影响您业务的术语、技术和趋势。
An early dial-up predecessor of the DSL family that can support up to 128 kbit/s symmetrical service. ISDN is a usage-based service offered by telephone companies that is being rapidly eclipsed by DSL. ISDN is a circuit-switched technology.
