Two interesting articles about radio tele switching which some use 198Khz for transmission. Deadline was for March 2020, changed to March 2021 and could be 2022, a movable feast. One problem it the lack of replacement RTS meters and Smart Meters not being ready to be rolled out.
https://www.energy-uk.org.uk/files/d...bruary2020.pdf
https://www.elexon.co.uk/smg-issue/issue-84/