ICAO Annex 14 regulation on Appendix 6-5, prescribes the use of medium intensity Aircraft Warning Lights (MIOL-AC) white flashing during the day (20.000cd) that becomes red steady burning during the night (2.000cd) and medium intensity red steady burning only for night mode (MIOL-C 2.000cd).
Depending on the height of the structure, the standard provides the use of two or more levels, which are intended to give a precise definition of the object and its size: for structures with a height up to 105 meters medium intensity warning lights (DUAL MIOL-AC) must be used at the top of the structure and medium intensity indicators at second (and last) level of the structure; while for structures with a height of up to 150 meters four levels of lights are required: the one at the top and the second one with medium intensity (Type AC) lights and the third one and the lower one with medium intensity (Type C) beacons.
If the structure exceeds 150 meters in height, it is possible to continue to use medium intensity Aircraft Warning Lights placed at regular intervals (as indicated in the table), but the structure must also be marked (painted with white / red horizontal bands). The alternative that the ICAO rule allows to use only AWLs, avoiding the marking with paint, is to use high intensity beacons (200.000cd in day mode), as indicated in Appendix 6-6; 6-7; 6-8.
Finally, if an aeronautical study or the civil aviation body under which the control of the structure in question falls, decides the use of other lights or other configurations, the prescriptions must be respected by way of derogation from the ICAO standard Annex 14.