It is SI and DI; seems to be their older model that they pair with the 9" units, but I think the GT56 is replacing it. It appears that when it is in the traditional mode, it runs on a frequency that doesn't overlap with the livescope. I don't know how it will work, but it only took a few minutes to strap it to the bottom of the TM, and if it doesn't work right I guess I can try something else.

It looks like they could make a cable to link 2 units together that would be plug and play, but I realize they aren't catering to people like me. I'll let you know how it works.

So I was right that there is indeed enough difference in the frequency of the livescope transducer and GT54 that they didn't interfere with each other with both of them on the same TM. I could split the screen and both worked fine. Unfortunately, the 2 GT54 transducers interfered with each other significantly, even though they were about 17' apart with one on the TM and the other on the transom. I don't believe there will be any way to use both, and I'm glad I didn't drill holes in my boat to mount the new one.

I just unplugged the one on the TM and used the new unit as a dedicated livescope. I might buy the stuff to build a network eventually, but right now I don't see the need for the kind of fishing I do. Thanks for the help!