Key to detailed test reports

Here are explanations for the technical terms in the iDTV summaries and some additional information.

Native resolution. The higher the figures the better. They apply only to LCD (and plasma) flat panel TVs, where the screens are made up of small dots called pixels (picture elements). The native resolution is the number of pixels horizontally by the number vertically and indicates the level of picture detail the screen can display. 850 x 480 is adequate for standard TV; much higher resolutions are needed for high definition (HD) broadcasts.

Technical performance. This is a summary of the results of technical tests on picture and sound quality and how well the iDTVs performed in weaker signal conditions.

PiP or PaP. Picture in Picture is the small picture in a corner of the screen showing what’s on elsewhere. Picture and Picture halves the screen to show two programmes at once.

UK languages for on-screen display/subtitles. Many digital TV tuners let you choose a language - when the broadcaster is transmitting these languages.

Channel list. This is a simple on-screen list of all the stations. You scroll down to select the TV or radio station you want. Simpler than using the on-screen TV guide or the numeric buttons, where you have to remember the channel or station number.

Can delete unwanted channels. Useful for removing TV channels you will never want.

PIP of current channel displayed in EPG. PiP means picture in picture. In this case it means that when you have the EPG on screen you also have a small picture in one corner of the screen showing the currently tuned channel. So you can continue watching while browsing the EPG.

Radio/TV button. Quickly switches the digital box between TV and radio stations. Without this you have to scroll all the way through the TV channel list to get to the radio channels.

Blank screen option. When listening to radio on an iDTV, the radio stations display their logo and brief programme information. Good thing to blank this TV picture to save energy and save aging the TV screen.

Audio description. When available this feature can decode extra spoken descriptions of what is happening on the screen – when these are broadcast. It is intended for people with visual impairment. Currently no iDTVs have this feature.

Timer recording. For digital TV recorder (PVR), timer recording is taken care of thanks to the on-screen TV guide and hard disc drive. With standard iDTVs, a similar process is possible. If you have a VCR or DVD recorder connected to the TV (see recording options) then it may be possible to get this combination to work like a PVR. Two things need to be in place and they depend on the products you have. The iDTV has to be able to send a special signal via the SCART lead when a selected programme starts and stops, and the recorder has to be able to respond to this signal. Many recent VCRs have this facility and most DVD recorders do. Unfortunately there are two types of signaling – link and video - so check when you buy that your iDTV and recorder are compatible. The system can work well but is clearly less convenient and flexible than a dedicated digital TV recorder.

AV connections. Check here for the types of socket available for connecting other equipment. For connecting a DVD player or additional set top boxes, a SCART socket with RGB input capability is best, although a SCART socket with S-Video capability can also give good results. A VCR requires only a standard video capable SCART. For a games machine or camcorder, look for a suitable front-mounted video or S-Video input. Some TVs also offer an HDMI input for digital video signals – use it for future High Definition TV channels or High Definition DVD systems.

Digital Audio output. Look out for this if you want to connect certain audio systems. In particular, it provides surround sound to home cinema systems, for some programmes.

Headphone socket. Useful if you want to watch TV without disturbing others in the room. Particularly useful if it offers independent volume control – so anyone hard of hearing can use headphones with the volume up.

5-Volt DC option on aerial input. This can be used with a few brands of amplified aerial (typically indoor aerials instead of connection to a separate mains supply. See our indoor aerial summaries for models that can be powered this way.

Automatic switching between widescreen and standard size. This is between full widescreen (16:9) used for most modern programmes and standard (4:3) when showing old programmes. Switching to 4:3 means the picture is not distorted (stretched) but it creates black bands left and right of the screen.

Best option for 4:3 switching. To avoid the black bands, some iDTVs can be set to auto-switch to a compromise mode, where the picture is both enlarged (zoomed) and gently stretched to fill the screen. Picture distortion is less than stretching it alone, but you lose a bit of the picture top and bottom.

Time to reboot. This is the time between switching on from standby and getting a picture – these iDTVs took between 8 and 25 seconds.

iDTV boots up to digital channel. Annoying if it automatically reverts to analogue – especially when analogue signals are switched off. With two of the iDTVs (the Grundig and Techwood), touching a number key to switch on took you to analogue TV.

Updates. Thanks to manufacturers for most of this information on how their TV will cope with future improvements and developments. Some boxes only allow manual updates – much less convenient because, to find out if one is scheduled, you would need to visit www.dtg.org.uk/retailer/download_schedule.pl and search for your brand of iDTV.

Freeview plan to launch improvements later this year. Some digital terrestrial boxes will take advantage of these changes through a firmware update. The manufacturers of other terrestrial boxes will instead launch new models to operate with them. See the more information summaries for what they told us of their plans.

Multiplex changes. A digital TV multiplex is a group of digital TV stations bundled together so that they all fit into one broadcast channel. At digital switchover some multiplexes will change, so digital terrestrial boxes will have to be re-tuned – some automatically and some manually. Check which in the more information summaries.

DTG Testing. The industry body Digital Television Group carries out testing of digital TV products, including for the 'digital tick'. You can be confident that a DTG tested digital product will carry on working through digital switchover.

MHEG5 v.1.06 is an updated industry standard that has been introduced in Autumn 2006. Some iDTVs will need firmware updates – we tell you which in the more information summaries.

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