Connecting the ASC (to control switches) and the TPC-400 to the legacy base

Old school, before Lionel decided to put their name, on the equipment. (IC Controls). Unfortunately, the same Lionel equipment, does not play well, with existing IC Controls devices, which are from ( at least 20 years ago).   A simple data wire pair, daisy chained, between each device works. Note: No more than the (8) devices pictured works.  Push the TMCC signal, past the (8 to 10) devices, pictured,  and the whole system goes south/quits.

Well I went ahead and experimented before I got any replies and what I did seems to have worked.

I spliced the the ASC and TPC DAT and COM leads together and then ran it into the Legacy base. I also spliced a wire coming from the DAT terminal on the TPC into the wire that goes into the binding post on the legacy base.

All of my switches, Legacy and and conventional locomotives both work great.

I think I'm good now.

The Legacy command base doesn't have the same drive current as the old TMCC command base, so if you get too many serial data devices attached, none of them will work.  One fairly cheap cure is buy the Z-Stuff DZ-2001 Data Driver.  It has plenty of drive for a multitude of serially connected devices.

Or get a SER2.

Yep, but I found an issue with the SER2 and the Z-Stuff DZ-2500 switches, so that's not universally good advice.

How many is too many serial data devices? What is an example of a serial data devices?

I only have the dz-1000s.

If I get an answer about the number of serial data devices, that will drive what I might do next - if anything.