AMR was originally designed so you can put all of the country specific bits and anything else you wanted onto a small card which plugged into a special slot. This would reduce the cost of the device because some of the parts would already be integrated with your motherboard.

In the UK anything that attaches to the phone line directly must be approved otherwise it is illegal to use it. So you can get your little AMR card design approved and not have to go through the hassle of approving your entire motherboard design as well.

CNR is the same type of thing but you've got network support as well.

- Trevor