A system provided to drivers to give an audiovisual indication in the cab of the status of the signal ahead. This system briefly works as follows; as the train approaches the signal it passes over a ramp between the rails, in which are placed two electromagnets (or a permanent magnet (see below), and an electromagnet). If the signal is green both magnets are detected by a receiver mounted between the axles. This causes a bell to ring and a warning disk shows a black aspect in the driver’s cab. If the signal is anything other than a green, only one magnet is detected which sounds a horn and a black and yellow aspect is shown. In this case the driver needs to accept the warning by pressing a button, otherwise the brakes will be automatically applied to stop the train.
