The new channel, later referred to as "Bulgarian Television" (BT) used the OIRT standard of 625 lines and 25 frames per second. It also used the D/K audio system, which was generally done to prevent reception of Western European stations in Eastern Bloc countries. Public attention was quickly caught by the new medium, and the number of bought and registered television sets increased gradually. In 1960, a powerful 20 kilowatt transmitter was installed at Botev Peak, covering a large area of the country. Later, more transmitters and retranslators were placed in various cities, towns and villages around the country.