DSM300 and dual transducers

[WarrenMudd]

I have now positively identified my 2 transducers: Airmar P66 and Airmar P39. I cannot locate any DSM300 module, although the stack of manuals I got from the PO has one. So I'm guessing both of the Airmars are cabled directly into the E80 Classic. Since the CF reader on the E80 is kaput, I'm replacing with Axiom 9. Is this an instance where I can use a "Y" cable adaptor? The P39 is plugged into the NMEA port on the back of the E80, and the P66 is plugged into the Seatalk port, and something else (GPS?) is networked into the SeatalkHS (Ethernet) port.