ISDN (short for Integrated Services Digital Network) is, unlike the analog voice services of old, a packet-switched digital solution that provides both voice and data transmission over a single line and delivers far better quality. It was born out of the need to move analog telehphone systems, which were unreliable, to digital. Here’s all you really need to know―ISDN can simultaneously transmit voice and data over traditional phone lines. There are 2 flavors of ISDN—BRI (Basic Rate Interface) and PRI (Primary Rate Interface). Don’t worry, we’ll be covering those.