# Commission Regulation (EC) No 262/2009 of 30 March 2009 laying down requirements for the coordinated allocation and use of Mode S interrogator codes for the single European sky (Text with EEA relevance), Division 4: Mode S interrogators, when operating with an SI code and if enabled by an appropriate operational parameter, shall be configurable by the operator to either:

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

not use lockout on the matching II code for transponders lacking SI code capability, or
use intermittent lockout on the matching II code for transponders lacking SI code capability.

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Source: https://www.legislation.gov.uk/eur/2009/262/annex/III/division/4 (the official version)
Page: https://openlegislation.uk/eu-regulation-2009-262/annex-III/division-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.