A diagram showing the principles of Absolute Block, with the traditional example signalboxes, A, B and C. A Up train travelling from A to C will see the signals in the order shown - signals in the Down direction are not shown.
<a href="https://en.wikipedia.org/wiki/User:Danny252" class="extiw" title="en:User:Danny252">Danny252</a> (<a href="https://en.wikipedia.org/wiki/User_talk:Danny252" class="extiw" title="en:User talk:Danny252">talk</a>)
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<span class="int-own-work" lang="en">Own work</span> (<span lang="en" dir="ltr">Original text: <i><bdi lang="">I (<a href="https://en.wikipedia.org/wiki/User:Danny252" class="extiw" title="en:User:Danny252">Danny252</a> (<a href="https://en.wikipedia.org/wiki/User_talk:Danny252" class="extiw" title="en:User talk:Danny252">talk</a>)) created this work entirely by myself.</bdi></i></span>)