The base card has no modules installed on board but can have up to 3 modules installed each supporting 8 BRI connections bringing the capacity of a single card to 24 ports.

This shows a side and front view of a BRI voice card with no modules attached.

Each 8 port module is fitted in the locations indicated on the diagram. With the first 8 channels in the left bay, channel 9-16 in the centre bay and channels 17-24 in the right hand bay.