Solution
You can connect only up to three separate NI PXIe-4339 modules simultaneously to the RM-4339; one to each position, given that RM-4339 is divided into three positions A, B, and C . Each of the three positions is independently controlled and powered by the NI PXIe-4339 to which it connects.
There are no constraints on how many or which positions are used. On the rear side of the RM-4339, the three 96-pin DIN connectors are labeled A, B, and C. These correspond to the three connector sets on the front of the RM-4339, which are also labeled A, B, and C. Connectors within one of these positions connect to the same NI PXIe-4339 module.
Refer to NI PXIe-4339 and RM-4339 User Guide and Terminal Block Specifications for more information.