Today"s network subscriber linecards handle many different functions by means of subgroups on the main board or individual modules. One of the most important functions of the main board is to provide distributed power to the subgroups or modules and switch them on and off in order to provide overvoltage / overcurrent protection and filtering, as well as to switch signals correctly. In many cases, the central power supply is part of the main board. Several dc-to-dc converters generate the individual voltages, either directly in or close to the application module as a point of load solution. This is the case for DSLAM, routers, xDSL, Ethernet, optical access, and PoE. Individual protection of data lines is essential to the safe operation of linecards.