BC – just in case you were not aware, you can add a DX Hub plugged directly into the built in SLink port of the Avantis to get the same functionality/capacity of the DX Link. Now you may need the built in port for something else and are still looking to expand the DX capacity further and this is a perfect use of the DX Link card. However you may not need to use up one of the I/O card slots if you can use the built in SLink port with the DX Hub.
As Nicola noted, the each individual DX connection offers up to 32×32 (ie bi-directional) channels. This can be either a single DX32 device, or two other DX devices linked in “cascade” mode. You can get either 4 DX connections when not using redundant connections, or 2 connections with redundancy (meaning you’ll still use all four connections, but in two redundant pairs).
DX connections can only be made to DX devices – currently that is the DX32, DX168, DX012, DX164-W, and DX88-P. It won’t work with anything else. (Not the ME personal monitoring system, AR/AB stageboxes, GX4816 stage box, nor other consoles, computers, etc).