CCIR System I is a 625-line analog broadcast television system used in the Republic of Ireland since 1962. It is a 625-line broadcasting standard targeting VHF Band I and Band III, sharing Band III with 405-line System A signals radiated in the north of the country.
The UK started its own 625-line television service in 1964 also using System I, but on UHF only; the UK has never used VHF for 625-line television, except for some cable relay distribution systems.
Since its debut, System I has been adopted by Hong Kong, Macau, the Falkland Islands, as well as South Africa. The Republic of Ireland has (slowly) extended its use to the UHF bands.
As of late 2012, analog television is no longer transmitted in either the UK or the Republic of Ireland. South Africa has discontinued System I in 2013, and Hong Kong will do the same in 2020.