For a an efficient use of the card, it is unavoidable to modify the F-Rom and to make an adjustment around IC23 allowing a a switching routine controlling the card.

So in a short time we had a number of routines available.
The most famous are the Branquartsystem, also used in the Atom in PC, and the CX-system.
In the western part of the Netherlands the CX-system (ClubExtension) was foremost in popularity. This under motto -CX the best there is- .

The CX_system see AN. 1985 nr.4 page 73/81
The Branquart_system zie AN. 1985 nr.4 page 58/72, and 1985-7/26

Experimenting it is inevitable to have the possibility of being able to use the Atom in his unmodified state.

Here is indicated how to do so with a simple switch.