Why does the black and white thing come up on in the corner of the screen when the adverts come on on itv?

The black and white box is merely an indicator to programmers as to when the part of the program will end. Not used in digital programming.
Updated on Friday, February 03 2012 at 03:10AM GMT
Source: Textperts
Collections: white boxprogrammerindicatoradvertisingitv