This work describes a sensor array based on optical emitters, which allows to detect
obstacles in railways. The sensorial system consists of a barrier of emitters and another of
receivers, placed at opposite sides of the railway. Apart from the disposition of the sensorial
system, it is necessary a codification method for the emission in order to detect the reception
or the non-reception of transmissions between an emitter and a receiver. The method is
based on a signal codification using complementary sequence pairs, suitably adapted for …