Editing Phase-locked loop (section)

===Clock recovery===
Some data streams, especially high-speed serial data streams (such as the raw stream of data from the magnetic head of a disk drive), are sent without an accompanying clock. The receiver generates a clock from an approximate frequency reference, and then uses a PLL to phase-align it to the data stream's [[signal edge]]s. This process is referred to as [[clock recovery]]. For this scheme to work, the data stream must have edges frequently-enough to correct any drift in the PLL's oscillator. Thus a [[line code]] with a hard upper bound on the maximum time between edges (e.g. [[8b/10b encoding]]) is typically used to encode the data.