The transducer ports are wired the same on the ETR 6/10N (aka BBFF1) and the DFF1, so not quite sure what is different. Both use pins 4 & 7 as the two temperature wires. When you have the DFF1 connected to the VX2, can you change modes (dual frequency or single HF or LF)? Maybe the DFF1 isn't communicating with the VX2. You can also tell if the DFF1 Stby light goes solid green after about 3 minutes...that means it doesn't see a NAVnet. If it remains blinking after about 3 minutes or you can change modes, then it is communicating.