What about those little yellow boxes in the middle of the tracks on
Adelaide suburban lines? They appear to detect the train as it passes over
them and turn the signals to red. How do they operate? Metal detectors like
at traffic lights, perhaps?
Muchas Gracias,
-- Adam Joyce 9706360s@magpie.magill.unisa.edu.au(When replying by e-mail please remove "NoSpam_" from e-mail address)