advert breaks

[decom]

What is the black and white rectangle in the corner of the tv screen before adverts for?

[dafyd]

originally, it was to warn the broadcaster that an ad break was coming and they would need to switch feeds from the programme to the adverts. i don't know if it still actually serves that purpose now everything is done digitally

[decom]

thanks. i just lost �10 tho. any other reasons for it would be appreciated.

[jenstar]

It still serves its original purpose on live shows so as to allow some flexibility in the placing of ad breaks. Pre-recorded shows of course have fixed points for ads that can be set-up in advance and therefore generally do not require the cue dots, as they're called.