A clock system includes a provisioning layer corresponding to a plurality of input clocks, and a plurality of layers arranged according to a hierarchy. The first layer in the hierarchy is operable to arrange the input clocks into groups and for each group select a corresponding group output clock. The...http://www.google.de/patents/US20020186718?utm_source=gb-gplus-sharePatent US20020186718 - Multi-layer control interface for clock switching in a communications element
