# Council Directive 92/91/EEC of 3 November 1992 concerning the minimum requirements for improving the safety and health protection of workers in the mineral-extracting industries through drilling (eleventh individual Directive within the meaning of Article 16 (1) of Directive 89/391/EEC), Division 4.2

Extent: E+W+S+N.I.

Such system must be capable of remaining operational in the event of an emergency.
The acoustic system should be supplemented by communication systems which are not reliant on vulnerable power supplies.

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Source: https://www.legislation.gov.uk/eudr/1992/91/annex/part/C/division/4/division/4.2 (the official version)
Page: https://openlegislation.uk/eu-directive-1992-91/annex/part-C/division-4/division-4.2
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.