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In the early years of television Irish viewers had access to the BBC via signals coming from Northern Ireland and Wales. By 1959 Northern Irish viewers had access to one public service broadcaster (BBC) and one commercial broadcaster (Ulster Television). The Secretary of the Department of Posts and Telegraphs - Leon O'Broin -had tried to progress the idea of an Irish channel since 1953, this new medium coming from the north was to spur the Irish government into action.〔Horgan, J. (2001) Irish Media: A Critical History Since 1922, 1st ed., London and New York, Routledge: p77〕 Teilifís Éireann began broadcasting on 31 December 1961. During these years many Irish radio listeners where listening to BBC Radio so the interest in BBC Television would continue, some had been watching since 1953 via spillover signals. 1963 saw the first cable service from RTÉ under the name RTÉ Relays, these tests were in preparation for the building of the Ballymun apartment blocks, which were built during these early years of RTÉ Television. RTÉ relays would opt to provide their service with the BBC and Ulster Television (later Cablelink would also provide HTV from Wales). == Technology == Ireland's cable television networks are primarily digital DVB-C services. However, in most areas, a small number (approximately 16) analogue channels are still carried alongside digital services. The legacy analogue cable television services provide unencrypted PAL System I television channels. Frequency plans vary from place to place and channels are carried in Band I, Band III, Hyperband and sometimes Band IV. In the past, additional encrypted premium analogue channels were also available. To view these channels a set top box was required. Cablelink / NTL Ireland used Cryptovision, while some other companies, notably Cork Multichannel, used Jerrold (General Instrument) scrambling systems. Cork City and other areas cabled by Cork Multichannel Television required an Jerrold (General Instrument)set top box for all channels. The entire Cork analogue cable network was encrypted from late 1980s onwards. The Cork network also carried more channels than other cable networks in Ireland at that time. When digital cable was launched in Cork, UPC Ireland rapidly swapped analogue set top boxes for digital boxes and then shutdown the analogue service entirely. The network still carries analogue terrestrial channels, RTE1, RTE2, TV3 and TG4 in some parts of the network. This means that Cork is the first city in Ireland with an exclusively digital cable network. For analogue cable in Ireland there is no set frequency plan. Most cable networks for analogue use Harmonically related carriers (carrier frequencies of exact 8 MHz multiples). Some cable networks such as Limerick use Irish terrestrial channel alignments or even a mixture of the two-channel plans. Digital cable operates using DVB-C, although encryption, as well as other platform details varies by provider. Most providers require the use of a set top box to view their television services. Some very small, independent, entirely analogue networks still exist. These use standard coaxial cables boosted and tapped at regular intervals. Unfortunately this can lead to serious signal degradation problems, particularly on overhead networks. Digital networks have far more sophisticated trunking systems. The five main Cities (Dublin, Cork, Galway, Limerick, and Waterford), along with towns like Longford, Dungarvan, Clonmel, Thurles, Kilkenny etc. now enjoy state of the art Hybrid fibre-coaxial networks which are used to deliver a myriad of services, including analogue and digital TV, broadband DOCSIS 3.0, and cable telephony services. Overhead cables are common in areas constructed before the foundation of the local cable firm, or where the cable firm did not have a construction agreement with the builders; underground cables are more common in developments build post-1985. Analogue MMDS specifications were legally set in 1998 by the then Office of the Director of Telecommunications Regulation in the document "Technical conditions for the operation of analogue programme services distribution systems in the frequency band 2500-2686 MHz" Virgin Media Digital MMDS uses a DVB-C variant on ex NTL MMDS and a variant of DVB-T on ex Chorus MMDS networks. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cable television in Ireland」の詳細全文を読む スポンサード リンク
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