5.110 in the Radio Frequency Table Allocation of Ireland.

Content Type
ITU FOOTNOTE
Title
5.110
Description
The frequencies 2 174.5 kHz, 4 177.5 kHz, 6 268 kHz, 8 376.5 kHz, 12 520 kHz and
16 695 kHz are used for the automatic connection system (ACS), as described in the most recent version of Recommendation ITU-R M.541. (WRC-23)
Source
https://search.itu.int/history/HistoryDigitalCollectionDocLibrary/1.43.48.en.101.pdf