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Clock recovery extracts a timing reference from a received signal so that a receiver can locate symbol boundaries.

Manchester encoding represents each data bit by two opposite half-bit levels. The compulsory midpoint transition supports clock recovery.

The bit rate counts data bits carried per second; the baud rate counts transmitted signal elements per second. A signal element need not carry one whole data bit. In Manchester encoding, each data bit occupies two half-bit signal elements, one high and one low. For example, choose low–high for zero and high–low for one. The compulsory transition in the middle provides a timing reference for clock recovery.

If one data bit lasts $T$ seconds, the bit rate is $1/T$, while each half-bit signal element lasts $T/2$. With this binary signal-element convention,Thus a 10 Mbit/s Manchester encoding signal uses 20 million half-bit signal elements per second. This is not a count of observed voltage transitions: some bit boundaries also contain a transition and others do not. Calling a whole two-element pattern a symbol gives a different symbol-counting convention; the physical fact is two half-bit elements per data bit.

In differential Manchester encoding, every data bit still has a compulsory transition at its midpoint for clock recovery. The data value is specified by whether a transition occurs at the beginning of the bit, rather than by the direction of the midpoint transition. One convention is beginning transition for zero and no beginning transition for one; interchanging the meanings consistently also works.

Reversing the signal polarity exchanges high and low everywhere, but preserves both the presence and the absence of transitions. A receiver using differential Manchester encoding therefore decodes the same data after a polarity reversal, provided it has acquired the timing and boundary reference. Ordinary Manchester encoding with a fixed low–high/high–low interpretation would exchange the two data values. The advantage is

A block code for line coding divides the data into five-bit groups and assigns each of the $2^5=32$ possible groups a distinct eight-bit codeword. The receiver reverses that assignment after finding the eight-bit boundaries. There are $2^8=256$ candidate codewords, so the designer has substantial freedom to select 32 suitable ones and reserve other patterns for control or synchronization.

The choice can limit long runs of equal bits to help clock recovery, balance high and low levels to reduce a persistent offset, and distinguish control patterns from data. These properties must hold across adjacent codeword boundaries too: two individually acceptable words can concatenate into an unacceptable run. The unused patterns can also help error detection and correction: an invalid received pattern exposes some errors, and the Hamming distance between valid codewords determines stronger guarantees. Redundancy alone does not imply that all errors are detected or correctable. Circuit complexity and propagation of a synchronization error also matter.

Before any further line coding or framing overhead, the useful fraction and expansion areThe three extra bits per five input bits are 60% overhead relative to the input, or 37.5% of the encoded output.