Read this: Ofcom - Television channels required to provide television access services in 2014

Summary: Published 280613 1.1 The Communications Act 2003 required Ofcom to publish a code setting out the obligations of television channels licensed in the UK to provide television access services. A copy of the current version of the Code, incorporating amendments made since the Code was first published, can be found at http//stakeholders.ofcom.org.uk/broadcasting/broadcast-codes/tv-access-services/code-tv-access-services-2013/. 1.2 The Code also provides for a mid-year review of the audience share and revenues of UK-licensed television channels, based on data for the previous year. - stakeholders.ofcom.org.uk