With the NN3D system, the hub101 should be used especially if you have more than one MFD. In the case of one MFD, it is okay to go off the shelf. The DFF1 most likely is setup for power sync provided by the NN3D HUB101. Check the MODE switches at the front. For off the shelf hub it should be DWN, UP, UP, DWN. Once the sounder powers up, you must run the wizard to find the sounder.