Sky viewing cards are usually "paired" with a particular box - that is the box and card are tied together by their serial numbers.
A card can only be paired with ONE box at any one time. To change the pairing you must call Sky and they will send out a signal to update the card and re-pair it with your specified box.
Here's a list of what is and what is not possible, depending on what type of card you have.
I beleive I have got this all correct, but sometimes this confuses even me! Please let me know if you think I have made a mistake
Watch Live TV
FTA Channels - No card necessary
FTV Channels - ANY card
Standard Pay Channels - ANY subscription card with a valid subscription to the required channel (no need to pair)
Premium Pay Channels - Paired card with a valid subscription to the required channel
Record TV - A card with the Sky+ features enabled PLUS:
FTA Channels - Any card
FTV Channels - Any paired card*
Standard Pay Channels - Any paired card* (Note: no need for valid subscription until playback)
Premium Pay Channels - Any paired card* (Note: no need for valid subscription until playback)
Playback Recordings - A card with the Sky+ features enabled PLUS:
FTA Channels - Any card
FTV Channels - Original card used to make recording* (Note: no need for pairing)
Standard Pay Channels - Original card used to make recording* with a CURRENTLY valid subscription to the channel (Note: no need for pairing)
Premium Pay Channels - Paired, original card used to make recording* with a CURRENTLY valid subscription to the channel (Note: MUST be paired)
*Otherwise recording interrupted displayed on playback
Definitions:
FTA (Free To Air) Channels - Those that can be watched without a viewing card (e.g. BBC, ITV etc)
FTV (Free To View) Channels - Those that are encrypted so require a viewing card to watch, but are not part of the Sky package so are free (e.g. C5 etc)
Standard Pay Channels - Sky Mix channels
Premium Pay Channels - Sky Movies and Sky Sports channels