1906 electrical transmission switching house above Llanberis, serving the Dinorwic, Glynrhonwy and Nantlle quarries, the Marconi wireless station and Caernarfon town. This was part of the Cwm Dyli transmission system, the earliest AC system in Britain. Currently repurposed as an emergency services communications relay station.

Reference: Information from John Rowlands, 2023.

RCAHMW, 2023.