What TV specification do I need for HDTV?
While some manufacturers outside the UK are making conventional CRT (Cathode Ray Tube) sets in HDTV mode, that seems unlikely to happen in the UK, given the current boom in sales of flat-screen TVs using either LCD (Liquid Crystal Display) or Plasma technology.

Our recommendation would certainly be that you buy a flat-screen TV if you want to future-proof yourself against HDTV (but click here to see if you need to). The thorny question is, however - what specification should you look for? (Scroll to the bottom of this FAQ if you just want the answer and want to avoid the technical explanation).

This issue is complicated - because so far there is no agreed European HDTV standard. To return to what we have in the UK at the moment, most TV sets use a 625-line standard - that is to say, the picture on your TV screen is effectively made up of 625 horizontal lines from top to bottom. What happens is that the picture (whether it has come from an analogue or a digital source) is 'painted' onto the screen line-by-line 50 times a second - fast enough for your eyes and brain to interpret what it sees as a smoothly moving image.

Actually, just to complicate things, there's a little cheat going on: all the odd-numbered lines (No.1, No.3, No.5, .... all the way to No.625) are re-painted 25 times a second and then all the even lines (all the way to line No.624) get the same treatment, and then it's back to the top to paint in the odd-numbered lines again. This is called 'interlaced' scanning.

If you scanned all the lines from 1-625 one-by-one, rather than alternately, that would be called 'progressive' scanning. And if you did that 25 times a second, your picture would look a lot better: because your TV set would effectively be giving your eyes and brain twice as much information per second (625 lines 25 times per second instead of half that number 25 times per second).

An HDTV signal uses one or more of three techniques to make the picture look better: it increases the number of lines to be scanned; and/or it uses progressive scanning instead of interlaced scanning; and/or it scans the lines at a faster rate (e.g. 50 times a second instead of 25).

The two techniques that HDTV broadcasters abroad tend to use most are called 1080i and 720p: that is to say, 1080 lines scanned in interlaced mode; and 720 lines scanned in progressive mode. In Europe, broadcasters and manufacturers have in effect agreed that either standard is acceptable, and have got together to approve something called the 'HD Ready' specification. In essence, this lays down that an 'HD Ready' set should comply with the following features:

1) Have a minimum display of 720 physical lines in wide aspect ratio - which means, in effect, that it needs to be at least 720 pixels deep and 1280 pixels across.

2) Use a DVI or HDMI interface which can accept either the 720p format or the 1080i format.

3) The DVI or HDMI interfaces need to support a copy protection scheme called HDCP.

(For the full spec click here)

If the TV set complies with the 'HD Ready' specification, then it is entitled to carry the 'HD Ready' logo (click here to see it - it's the one on the right).

So, to cut to the chase, if you want your new TV to be HDTV-ready, look for an HD-Ready logo. Because the logo is very new, it is theoretically possible that there are TV sets in the shops that already meet this specification, but don't sport the logo. But check the specs very carefully to see that the display in question does indeed meet all the above criteria. Many flat-screen displays today don't, and the thing they fall down on is likely to be the HDMI or DVI connectors rather than the screen resolution.