The demand for faster internet access, coming from both private and business customers, is getting higher and higher. But not only the higher data rate, but cheaper and more flexible access via the normal analog telephone is required. Slogans like Voice over IP (VoIP), Voice over ATM (VoATM) and Voice over DSL (VoDSL) are becoming more and more popular. In most cases however, only the digital side and data processing side is considered for these new emerging technologies. In addition to the required protocols and packetizing, other design factors have to be taken into consideration. This lecture describes the requirement for the analog POTS interface in systems, like Integrated Access Devices (IAD) and xDSL-Network Terminations (xDSL-NT). These two very similar applications will dominate the next few years in the telecommunication area. An overview of the architecture is given. Especial phenomena like echoes will be shown together with solutions for that kind of problems. Further Infineon's DuSLIC chipset is shown that represents an optimal solution for the POTS interface of such systems.