The Digital TV Group (DTG) [1] is the industry association for Digital Television in the United Kingdom : The Group was formed in 1995 to set technical standards for the implementation of digital terrestrial television in the UK (known as the D-book) and now encompasses all digital TV platforms and convergence issues. The DTG’s members are companies and organisations involved in digital television.

The Group operates a test centre (DTG Testing) which ensures manufacturer’s products conformance to D-Book specification - allowing them to use the Freeview, Freeview Plus and Digital Tick logos. The centre also offers access to the UK’s over-air download channel.

The Group published the sixth edition of the D-book in March 2009. D-Book 6 includes the detailed specification for high definition television services on the UK Freeview platform.

In March 2011 the Group published D-Book 7: the detailed interoperability specification for digital terrestrial television with extended Connected TV functionality. D-Book 7 provides the baseline specification that YouView, Sky, Virgin Media and others can build on for trademark requirements to support their services.

Digital television (DTV) is the transmission of audio and video by digitally processed and multiplexed signal, in contrast to the totally analog and channel separated signals used by analog TV. It is an innovative service that represents a significant evolution in television technology since color television in the 1950s. Many countries are replacing broadcast analog television with digital television to allow other uses of the television radio spectrum. Several regions of the world are in different stages of adaptation and are implementing different broadcasting standards. There are four different digital television terrestrial broadcasting standards (DTTB) and they are: Advanced Television System Commitee (ATSC) is a system that utilizes 8 level vestigial sideband (8 VSB) for terestrial broadcasting. This standard has been adopted in the United States and in other countries. Digital Video Broadcasting-Terestrial (DVB-T) is that utilizes coded orthogonal frequency-division multiplexing (C-OFDM) modulation and supports hierarchical transmition. This standard has been adapted in Europe. Terestrial Integrated Services Digital Broadcasting (ISDB-T) is a system designed to provide good reception to fix receivers and also portable or mobile receivers. It utilizes OFDM and two-dimensional interleaving. It supports hierarchical transmition of up to three layers and utilizes MPEG-2 video and advanced audio coding. This standard has been adopted in Japan. Digital Terestrial Multimedia Broadcasting (DTMB) adopts time-domain synchronous(TDS)- OFDM technology utilizing a pseudo random signal frame to serve as the guard interval (GI) of the OFDM block and the traning symbol. The DTMB standard has been adopted in the People's Republic of China (PRC), including Hong Kong and Macau.