Block code: Difference between revisions

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In [[information theory]], a '''block code''' is a [[code]] which encodes strings formed from an alphabet set <math>S</math> into code words by encoding each letter of <math>S</math> separately. Let <math>(k_1,k_2,\ldots,k_m)</math> be a sequence of [[natural numbers]] each less than <math>|S|</math>. If <math>S={s_1,s_2,\ldots,s_n}</math> and a particular word <math>W</math> is written as <math>W=s_{k_1}s_{k_2}\ldots s_{k_m}</math>, then the code word corresponding to <math>W</math>, namely <math>C(W)</math>, is

The '''Railway Block Code''' is a system of bells used to send simple messages about [[train]] operations from one signalbox to another. For example:

* 1 bell - attention

<math>C(W) = C(s_{k_1})C(s_{k_2})\ldots C(s_{k_m})</math>.

* 2 bells - train depart

* 1 - 2 - 1 bells - light engine

* 4 bells - passenger train

* 3 bells - train arrive