[Tristan]

Chris T got it pretty much spot on. NTL -- as with all the other digital providers -- sends the channels in bunches called transport streams, or multiplexes (you will see this term a lot on DTT sites).

On cable, every transport stream carries EPG information for every channel for the current day. This is in contrast to Sky, where the transport stream only carries information for the channels on that stream -- this is why the Mini Guide doesn't work properly* on Sky boxes, and why they can't have a mini-TV on their full Guide screen.

To save bandwidth on cable, there is only one TS that carries all the information for all three days. This is the same one that carries the Front Row preview channel -- so when the box has to switch streams to get the new data, it switches over the mini TV, too.

The reason it's three days rather than seven or eight is, as has been pointed out, due to the limited RAM in the older boxes, and due to the enormous length of time it would take for the box to gather data for seven days (it's bad enough with just three!). Just be thankful you're not on Telewest -- they only have the current day, and that's it.


* Well, it explains why you can only get info for the current programme, and not any others. It doesn't explain why Sky's UI designers think you need to press left and right to go up and down...