A system that gives trackside staff audible warningAn audible tone or bell that is sounded when the Level Crossing protection system is activated. See also Yodalarm. of the approach of trains
by means of ‘safe’ and ‘warning’ tones, activated by the Signalling SystemA series of electrical, electronic, electro-mechanical units brought together to form a system which controls the safe movement of trains.
to enable them to reach a place of safety. Obsolescent system – see also
Automatic Track Warning System.