 In August 1906, power from Cwm Dyli was used to power the Oakeley Quarry in Blaenau Ffestiniog carried over the Crimea Pass by a long overhead transmission line at 10,000 volts.Cwm Dyli was claimed to be the largest electricity generating plant of its kind in Great Britain at the time.Electricity produced here was also used to power the Long Wave Wireless Telegraph transmitting station built by Marconi in 1912 near Waunfawr.