Lars, quoted from FB comments, says:
The number of frame synchronizers in a system you need is equal to the number of input sources minus one. So with Chromagnon + Visual Cortex, you can have two external sources. One is the master timing reference, and the other is frame synchronized by Chromagnon’s TBC. Key to the Automata series concept is that all units include a TBC and a 2:1 RGB function. Meaning each device can mix itself into an external source. RGB inputs are separate from the decoder/TBC section. Yes, you can feed the outputs back through the TBC in feedback mode while still using the RGB inputs.
Visual Cortex locks itself to the timing of an external source. That external source can also be fed to an input decoder, so you can patch the video through the system. Visual Cortex has to slave itself to the external timing in order for this to work. Chromagnon locks itself to the timing of an external source via the genlock input (or not, can be free running). Where it differs is that the input decoder has a TBC/frame sync this time. So the external sync/genlock source and the external video source don’t have to be one in the same. Meaning we can sync Chromagnon #2 to Chromagnon #1, while both of them can frame sync an asynchronous external video feed, resulting in two synchronous external input channels. So technically Chromagnon has two external inputs (Genlock/Sync Input and External Video inputs). Whereas Visual Cortex only has one (Input Decoder and Genlock/Sync Generator must be the same).