Hello,
Our group has a DR-1X repeater in stand alone Fusion mode and we link it via RF to an FTM100 node into the Fusion network. I presume you are NOT asking about this but wanted I to give a little background.
If you are wanting to connect the DR-1X to another radio (such as the FTM100) for an external link radio it seems you will need , at least, a basic controller that will accept the COR, TX/RX audio and PTT signals and feed them between the two. The DR-1x has a connector at the rear that has all the signals needed to connect to an external controller. You can , most likely , obtain the same needed signals on the FTM100 from the Data jack on the rear.
Look into the Repeater Builder website for info on controllers.
73,
Ke6jz