[entwisi]

the calculator thingy is a pin generator. what you do is when you want to do certain transactions ( usually around setting up payments and transfers), you put your debit card or in nat wests case it sounds like they send you some other card in it, enter your PIN and it generates a seemingly random number. teh internet site won't let you set up a payment etc without this generated number. The idea is that even if someone got your internet bank details and logged on as you they couldn't transfer all your money out without this gadget and your bank card. Its another layer of security. Barclays were the first to do this and won an award in teh internet security presentations(thinkk Bafta tyoe thing) for it.