 Wherever a serial communication channel does not transmit the clock signal along with the data stream, the clock must be regenerated at the receiver, using the timing information from the data stream.Clock recovery is a common component of systems communicating over wires, optical fibers, or by radio.Some digital data streams, especially high-speed serial data streams (such as the raw stream of data from the magnetic head of a disk drive and serial communication networks such as Ethernet) are sent without an accompanying clock signal.