This issue seemed different enough from "multiple serial ports" thread that I decided to start afresh.

I'm looking to build a box that will take output from a GPS and send the output to 3-4 devices (Empeg, APRS-capable radio, laptop and ???). One-way only, so would seem I would need TX+GRND only, true?

This is not really a multiplexer in the way that I think of a mux or demux, maybe a "splitter". I found a commercial version of what I am after here but it is primarily RS422. I doubt that under the epoxy, that unit is very complicated. I found a few other units, too, but they were intended for automation use and were way too big and expensive.

Can anyone take a stab at what would be involved, circuitry-wise, in a home-brew solution? If this was TX-only, might is be possible to just physically split the RS-232 output or would some kind of amplification likely be required?