# Level Crossing (Trummery) Order (Northern Ireland) 2004, Paragraph 10


The audible alarm shall sound if:
(a) any barrier is horizontally dislocated when in the fully-lowered position;
(b) the main power supply fails;
(c) all the red traffic light signals facing in one direction fail.

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Source: https://www.legislation.gov.uk/nisr/2004/244/schedule/2/paragraph/10 (the official version)
Page: https://openlegislation.uk/level-crossing-trummery-order-northern-ireland-2004/schedule-2/paragraph-10
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.