Television is the encrypted or unencrypted transmission of non-permanent images, with or without sound, through an electronic communications network, intended for simultaneous reception by the general public.
For decades, this transmission has been based on analogue technology. However, innovation and development have provided more effective means for recording, storing and processing electrical signals, as well as the possibility of transmission in digital form. This has led to the development of digital television, which offers considerably better quality and allows space for a larger number of TV channels, as well as other capabilities.
In the European Union, it was decided that analogue terrestrial broadcasting should be discontinued by 2012, which led Member States to prepare for the transition from analogue to digital television. Taking place in phases, the transition to digital terrestrial television (DTT) in Portugal was accomplished on 26 April 2012.
See ANACOM's decisionshttps://www.anacom.pt/render.jsp?categoryId=377159 on digital television.