Illustration of the functionning of <a href="https://en.wikipedia.org/wiki/European_Train_Control_System" class="extiw" title="en:European Train Control System">ETCS</a> Level 1
<a href="//commons.wikimedia.org/wiki/User:Fran%C3%A7ois_Melchior" title="User:François Melchior">François Melchior</a>
CC BY-SA 3.0
Own work, inspirated by <a href="//commons.wikimedia.org/wiki/File:Etcs_l1.jpg" title="File:Etcs l1.jpg">Image:Etcs l1.jpg</a>