Analogue, and 4:3 programmes on digital, are broadcast in 4:3. (14:9 programmes are letterboxed within the 4:3 frame; also many films are now broadcast on analogue as letterboxed 16:9 within a 4:3 picture). 16:9 widescreen programmes are generally broadcast on digital as Full Height Anamorphic pictures, meaning that all the information is compressed into a 4:3 picture. View this on a 4:3 set in its natural format and you'll see the whole picture, but squashed up. The digibox can process this in various ways - it can reformat 16:9 FHA so that it appears as letterboxed 16:9 within a 4:3 frame for 4:3 TVs, or it can crop the 16:9 image by taking the sides off, producing an unsquashed picture (but with bits missing), or just send the signal straight through to the TV in FHA format. It also sends a signal to widescreen TVs to indicate the correct format, which can be overridden by the viewer.