The Add-on Network Interface Module (NIM) can be added to a base system to allow for adding an additional 32 hardware items to the network. This module can only be added to a base system, it can not act as a base system itself. A base system can support up to 15 add-on NIM's. Each NIM itself can support up to 500' of cable (with up to 32 hardware items along it's length). With this item it's technically possible to have over 500 hardware items on a single system with about a half of mile of cable. This is a USB device and is connected directly to the computer with a USB cable. Each Network Interface Module can provide 750mA of power to the hardware. The product pages for the sensors and controls lists the mA of power that the module uses. 

Important Notes: The Add-on NIM's connect to the computer in the same way as the primary NIM. They shouldn't be connected inline with another NIM. While they are completely isolated from other NIM's to the software all the NIM's appear as one big network. 

This Network Interface Module is not compatible with legacy hardware. Legacy hardware is any hardware shipped before May 2017.