The early cardFollowing the problems with upgrading the BBC micro to use Econet - namely it is fiddly, takes space on the motherboard, and cannot be performed by all users due to the need to solder - Acorn devised the network card. This had the added benefit that if something trashed the line drivers or went further and affected the ADLC, simply take out the damaged card and fit a new one.
The Econet module expansion cards were to be used interchangably in:
Here is a scan of an early style network card. I apologise for the blurriness, however my scanner has extremely precise focusing...