Basic, old fashioned CRT (Cathode ray tube) type TV's are 480i. The 480 means that there are 480 lines of "light" hitting the screen of your TV from behind (counting from bottom to top). Now let's call the very bottom-most line, line 1, the one above line 2 and so on, okay?


The 'i' indictor means "interlaced". The problem with old analogue TV signals is that they can't carry very much data at one time (they have a small "bandwidth"), which makes it difficult to reliably get 480 lines of data to your TV at once. Instead, they actually only broadcast half of the signal, (lines 1, 3, 5, etc) and then right after that the other half (line 2, 4, 6 etc) in a separate transmission. If your TV keeps alternating the picture between odd and even lines fast enough, you don't see much of a difference. It is therefore “interlacing” the two separate pictures of 240 line each.


The other type of indicator you may have seen is 'p' (which stands for progressive), this means that the device is showing you all of the lines all of the time. That is to say instead of updating lines 1, 3, 5 and then 2, 4, 6, it updates 1, 2, 3, 4, 5, 6, all at once which makes for a much smoother looking picture, especially when your are watching something with a lot of fast movement like an action movie.


The screen resolution will also tell you the number of lines on the TV screen (for example if your screen was 1920 x 1080 this would be a resolution of 1080 lines top to bottom).


There are three "defintions" for TV types, Standard Definition (SD), Enhanced Definition (ED) and High Definition (HD). SD simply means 480i (480 lines, not all shown at once). ED means 480p (480 lines, all seen at once). So, anything that's left (anything with more than 480 lines) is considered HD.


Therefore because progressive is the best way to deliver a signal and 1080 lines is the highest number of lines in use today, a 1080p TV will future proof you and provide the highest quality picture options depending on the signal it is supplied with. These are much more affordable now so unless you are looking for a real budget unit I wouldn't buy anything else.


For a long time LCD and Plasma HDTVs only came in 720p (unless you had LOTS of money to burn), but more and more 1080p sets are now out there, and at very reasonable prices, almost all projection TVs produced new now are 1080p. It's worth noting that some LCD displays offer even higher resolutions than 1080, but this offers no improvement in picture quality and in fact may actually detract from it. It's also worth noting that under fast movement LCD resolution does not stay stable, so 1080 lines could well end up being less than 700!


Now let's move onto how we get that HD picture to your TV. Just like music, your picture quality will only be as good as your weakest component. If you are listening to an old audio cassette, it doesn't make much difference how expensive your sound setup is, you are not going to get great quality music. The same is true of TV.


People generally get their TV one of 3 ways, Cable, Satellite or the Free over-the-air kind.


All of these ways of receiving TV offer HD content (they broadcast a digital signal that can carry HD information, separate to the analogue signal that older TVs pick up). Most cable and sat providers can rent you an "HD Box" that will allow you access their HD content and Freeview HD will get here eventually.


Those broadcasting HD may broadcast some shows in 720 lines, but most now come in 1080i. You should beware that in order to "save space" both cable and satellite providers compress their HD signals. Decompressing these signals for you to see is what their "HD Box" is doing (just like ZIPing a computer file). You will inevitably lose some picture quality due to this compression process but for most people the difference is minimal.


You can watch a 1080 signal on a 480 digital set if you want but you will of course lose some of the detail. Likewise, you can watch a 480 broadcast on a 1080 set. In this case your TV actually has a small "brain" inside it, which creates new lines to make a full 1080 image (it looks at the colors above and below the line it is creating and guesses what should go in the middle). This process is called "up-scaling". If you are going to be watching a lot of regular DVDs (which are in 480p as long as you have a "Progressive Scan" DVD player) then how well the TV up-converts should be a key question you want answered before you buy, although more and more people now are using Dvd players with built in scalers to give your older Dvds a higher grade looking output. Just remember though, that a Dvd player that outputs 1080 from standard Dvd is not a HD Dvd player.


Although 1080p sets can play up to 1080p signals, there are no broadcasts out there in any definition better than 1080i right now (and due to bandwidth restrictions, there won’t be for some time yet). However your 1080p ability comes into play with the new High Definition DVD formats (HD DVD and Blu Ray DVD). These both send out a 1080p signal, for the best picture quality possible.


In short, when you are out and about, try to look at any 1080p TV. If you are looking at it in a shop try to see if they can show you a standard 480 signal on it as well as HD to see how it handles both types of signal. LCD screens in particular are very poor at showing lower resolution pictures. Ironically good old fashion CRT TV's do a better job of that than anything new!


I hope this helps!